JPH09186739A - Packet communication system and packet communication control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication control method in which waste of re- transmission of a packet by a transmitter side because of not in time of an acknowledge regardless of reception of a packet normally and deteriorated throughput due to hindrance of consecutive transmission of packets is avoided because of occurrence of expiration of time by dividing data into a size with a shorter time for transmission of the packet sent by a terminal equipment than the expiration of time of a re-transmission timer and processing the divided data into a packet. SOLUTION: A timer section 104 starts a re-transmission timer at transmission for each transmission packet to check whether or not reception acknowledge is received within the expiration of time and to measure a round trip time and to calculate the expiration of time based on the measured round trip time. A packet output section 103 divides the packet length of the packet to be sent so as to generate packets so that the acknowledge is received within the expiration time of the re-transmission timer based on them above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packet communication system for packetizing and transmitting and receiving data, and in particular, it is possible to suppress a decrease in throughput due to occurrence of a packet retransmission due to a timeout due to a delay in acknowledgment. And a packet communication control method.

[0002]

2. Description of the Related Art In order to share information among a plurality of computers or to decentralize data processing, data communication has conventionally been performed between computers via a network. And most of the data communication employs the packet communication method. The packet communication system is a communication system in which data is packetized and transmitted / received, and is a system suitable for decentralized communication control.

For example, communication between computers known as the Internet will be described.
On the Internet, for example, a connectionless high-speed transmission line known as Ethernet and a connection-type transmission line for setting a connection prior to communication like a conventional telephone network can be used. In either case, data is stored and transmitted / received on the transmission path in a packet called an IP (Internet Protocol) datagram having a format as shown in FIG.

However, when an IP datagram is transmitted through a transmission line, data may be erroneous due to noise or collision between packets. Furthermore, there is a risk that the packet will be delivered to a terminal different from the original destination. This is because an error occurs in the header in which control information such as the destination of the packet is written, and when such a situation occurs, the packet may be delivered to a terminal different from the original destination.

For this reason, among the terminals that exchange data using the IP datagram, the terminal that receives the packet containing the data sends an acknowledgment to the packet to the transmitting terminal. TCP (Transmission Control Protocol), which is a protocol for acknowledgment
(See FIG. 13)) is generally used.

In the communication using TCP, the transmitting terminal determines that the correct data has not arrived at the partner terminal when the acknowledgment cannot be received within the time-out period after the data is packetized and transmitted by itself. Then, the same data is packetized and transmitted again (see FIG. 14A).

At this time, it is preferable that the time-out period serving as a criterion for determination is ideally set to a time period when a confirmation response should be received when correct data is received by the partner terminal. However, we cannot know exactly this time.

Therefore, it is usual to set a timeout time larger than the estimated time in order to allow a margin after estimating the time when the confirmation response should be received. This is because if the timeout time is set without any allowance, even if the receiving terminal receives correct data and sends an acknowledgment, it may be affected by fluctuations in the processing load of the terminal or fluctuations in traffic in the network. The reason is that it often happens that a confirmation response cannot be passed by the time-out period, which makes it necessary to try to retransmit a packet. This is a waste of communication resources and is a waste of time.

On the other hand, if the time-out time is set too large by giving too much margin, it takes a long time to judge the correct data and retransmit the packet when the correct data does not reach the other terminal. After all, the throughput will decrease.

For this reason, in TCP, the round trip time, which is the time from packetizing and transmitting the data to receiving the confirmation response, is sequentially measured, and the time transition of the round trip time is taken into consideration. Estimate the round trip time of the packet to be transmitted next.

Then, the timeout time of the packet to be transmitted next is calculated based on the estimated round trip time. For example, in IETF RFC 793, the measured round trip time (RTTovs)
And the estimated round trip time (RTT)
pre), the new estimated round trip time (R
TT) is calculated, and the timeout time (RTO) is calculated based on RTT.

RTT = αRTTpre + (1-α) RTTovs RTO = βRTT, (β> 1) where α is (0 ≦ α ≦ 1) (1) Round trip time estimation and timeout in the positive acknowledgment protocol Many of the conventional methods for calculating time are assumed to be used on a relatively high-speed transmission line such as Ethernet. In this case, the round trip time is the processing load on the computer along the way, Network utilization has a major impact.

However, assuming the use in a public network or a mobile communication network, the transmission speed is extremely low (slow) as compared with Ethernet, so that the round trip time is
It is affected by the size of each packet received. That is, when a large packet is transmitted / received on a low-speed transmission path, the time required for transmitting the packet is large in the round trip time. On the other hand, as a method of estimating the round trip time and calculating the timeout time for the round trip time with a larger variance, Jacobson (V) uses “Congestion Av
oidance and Control, ”Computer Communication Revie
In the literature of w, vol.18, no.4, pp314-329 (Aug.), it is recommended to use the following formula (2).

Then, by using the method of equation (2),
If the size of the transmission packet or the reception packet is dispersed, an appropriate timeout time can be set.

DIF = RTTovs-RTTpre RTT = RTTpre + g * DIFDEV = DEVpre + h (| DIF | -DEVpre) (1/8 is recommended as the value of g and 1/4 is recommended as the value of h) RTO = RTT + 4 × DEV (2) Here, DIF represents the difference between the estimated round trip time and the measured round trip time, and DEVpre is the estimated value of the round trip time up to that point. , And DEV is the deviation of the estimated round trip time.

On the other hand, when error correction is performed on a transmission line or in a wired communication line using an optical fiber, an error is rarely generated in a packet. Therefore, after the data is packetized and transmitted, a time-out time is set. It is conceivable that the reason why the acknowledgment cannot be received before the arrival is due to congestion. Therefore, in TCP, when a timeout occurs, error recovery by retransmission is performed, and at the same time, a procedure for avoiding congestion known as slow start is executed.

Therefore, once a time-out occurs,
It becomes impossible to continuously transmit packets, and throughput is reduced.

[0018]

In a terminal such as a computer, when the transmission speed of data to be received by the terminal is higher than the transmission speed of transmission data from the terminal, or when the transmission speed is upstream transmission. When the transmission line and the downlink transmission line are connected to an asymmetrical transmission line, especially when the speed of transmitting the data transmitted from the terminal is slower than that of Ethernet, that is, in the case of a narrow band transmission line, The round trip time largely depends on the transmission time of the packet transmitted by the terminal and is not significantly affected by the transmission time of the packet received by the terminal.

If the size of the packet transmitted from the terminal is sufficiently small as compared with the maximum packet length that can be transmitted from the terminal, if the size of the packet received by the terminal continues. Regardless, it is estimated that the round trip time is short, and the timeout time is accordingly set small.

When the terminal transmits a large packet such as the maximum packet in this state, the time required for the transmission of the packet is long. Therefore, even if the data of the packet is actually delivered to the partner terminal within the timeout time. The confirmation response may not be received.

In this case, this large packet is transmitted again, and as a result, the narrow-band transmission path is wasted, resulting in a decrease in throughput and a delay in data transmission.

In a protocol such as TCP, when a terminal receives a packet containing data, it waits for an acknowledgment to send an acknowledgment to the partner terminal, and data to be sent to the same partner terminal is sent. In some cases, the data and the acknowledgment are packetized in the same packet and transmitted.

When the created packet is large, for example, the maximum packet, the confirmation response may not arrive within the timeout time at the partner terminal due to the above-mentioned reason.

At this time, if the above-mentioned procedure for avoiding congestion is executed, packet transmission is restricted at the partner terminal, so that packets cannot be transmitted continuously. Therefore, there is a problem that the terminal cannot receive data at high speed.

Therefore, the packet transmitted from the transmitting side is
There is a strong demand for the development of a technology that can rationally eliminate the waste of retransmission of a packet due to a timeout when it reaches the receiving side.

In view of the above, according to the present invention, the speed at which a terminal such as a computer transmits data received by the terminal is
A packet that can transmit correct data using the positive acknowledgment protocol even when connected to a transmission line that is faster than the transmission speed of the data transmitted from the terminal, that is, is asymmetric with respect to the transmission speed. A basic object of the present invention is to provide a communication control method, and a first object of the present invention is to enable a confirmation response to be correctly received even if a conventionally used timeout time calculation method is used. To do.

A second object of the present invention is to enable a terminal to continuously and rapidly receive data. A third object of the present invention is to efficiently use a narrow band transmission line for transmitting data transmitted by a terminal.

A fourth object of the present invention is to prevent wasteful use of a transmission line for receiving data by a terminal and a narrow band transmission line for transmitting data transmitted by the terminal.

A fifth object of the present invention is to provide a packet communication terminal which realizes the packet communication control methods of the first to fourth inventions described above.

[0030]

In order to solve the above problems, the present invention is as follows.

According to a first aspect of the present invention, a terminal connected to a transmission path in which the transmission speed of data to be received by a terminal is higher than the transmission speed of transmission data from the terminal, packetizes and transmits the data. In packet communication control,
The size that the time required to transmit the packet transmitted by the terminal is shorter than the timeout time of the retransmission timer, which is sequentially calculated from the measured value of the round trip time required from transmitting each packet to receiving the acknowledgment. The point is to divide the data into packets and packetize them.

According to a second aspect of the invention, a terminal connected to a transmission line in which the data transmitted by the terminal is transmitted at a higher speed than the data transmitted by the terminal is packetized. When the terminal receives a packet and waits for an acknowledgment to be transmitted, the time required to transmit the packet transmitted by the terminal is shorter than a predetermined time. The point is to divide the data into packets and packetize them.

According to a third aspect of the present invention, a terminal connected to a transmission line in which the data received by the terminal is transmitted at a higher speed than the data transmitted by the terminal is packetized. A control method used in packet communication in which the next transmission is performed based on the measured round trip time from the transmission of each packet to the receipt of an acknowledgment and the size of the packet to be transmitted next. The point is to decide the timeout time of the retransmission timer for the packets to be transmitted.

According to a fourth aspect of the present invention, a terminal connected to a transmission path in which the data received by the terminal is transmitted at a higher speed than the data transmitted by the terminal is packetized. A control method used in packet communication for transmission by transmitting the packet, the measurement value of the round trip time required from transmitting each packet to receiving an acknowledgment and the transmission of the maximum packet that the terminal can transmit. The gist is to determine the timeout time of the packet to be transmitted next based on the time.

A fifth aspect of the present invention is a communication system using a transmission line in which the transmission speed of data to be received by a terminal is higher than the transmission speed of transmission data from the terminal, Data is sent and received between packets and transmitted, and when a packet is received, an acknowledgment is returned, and when a packet is sent, the retransmission timer starts counting and confirmation from the receiving side by the elapse of a predetermined timeout time. In a packet communication system that attempts to retransmit a packet when there is no response, the data to be transmitted is packetized and output, and the transmission packet length is optimized based on the given timeout time information. A packet transmission unit that divides data into packets and sends them to the transmission line, and a packet reception unit that receives packets from the transmission line And to measure the round-trip time to the acknowledgment from the transmission of the packet is received,
A timer unit having a retransmission timer function for determining the time-out period based on this round-trip time, giving the time-out period information to the packet transmitting unit, and measuring the time elapsed after each packet is transmitted. It is equipped with.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is a communication system using a transmission line in which the transmission speed of data sent to a terminal is higher than the transmission speed of data sent from the terminal, and the data to be transmitted is Packetization is performed, and when a packet is received, an acknowledgment is returned, and when a packet is sent, the retransmission timer starts counting, and if there is no acknowledgment from the receiving side before the elapse of a predetermined timeout time, the packet is retransmitted. In an attempted packet communication system, the packet is transmitted so that the acknowledgment can be received within the timeout time of the retransmission timer determined from the measured value of the round trip time required from the transmission of each packet to the reception of the acknowledgment. It is characterized by shortening the packet length of the packet, and the length of the packet to be transmitted. And long, so that the situation can not return an acknowledgment before the timeout period does not occur,
The transmission of long data is divided into short packets and transmitted in a plurality of times, or a timeout is lengthened depending on the packet length to prevent a timeout.

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

(Basic Configuration of System) First, the basic configuration of the entire system to which the present invention is applied will be described.

The present invention assumes a system using an asymmetrical transmission line in which a large amount of data is transmitted through a high-speed transmission line and an acknowledgment response from the side receiving this data is returned through a low-speed transmission line. We aim to rationally solve the problem in that case. Various examples of using such an asymmetrical transmission line are conceivable, such as properly using Ethernet and public telephone network.

That is, an intelligent terminal such as a computer is used as a terminal, and it is connected to the network.
It is assumed that data will be exchanged with the host system connected to the network. The connection between the network to which the host system is connected and the terminal is configured as shown in FIG. 1, for example.

In FIG. 1, 1 is a terminal, 2 is a terminal adapter, 3 is a network, and 4 is a network adapter. The terminal adapter 2 is an interface for wireless communication connected to the terminal 1, and has a function of wirelessly exchanging information with the other party and passing the information to the terminal 1, converting the transmission information from the terminal 1 into a radio signal and transmitting it. I have. The network adapter 4 is an interface for wireless communication that is connected to the network 3. The network adapter 4 wirelessly exchanges information with the terminal side and transfers it to the network 3 to convert transmission information from the network 3 to the terminal into a wireless signal. It has a function of transmitting.

FIG. 1 shows a configuration in which, for example, a portable computer is used as the terminal 1, a card-type removable terminal adapter 2 is provided in the terminal 1, and a network adapter 4 is connected to the network 3. ing. The terminal 1 is connected to the network 3 via the terminal adapter 2 and the network adapter 4.

As the network 3, Ethernet or A
It is conceivable to use a high-speed network used in a communication network such as an existing LAN or B-ISDN such as TM. Then, in these transmission paths, the Ethernet packet or the PPP described in RFC1171 / 172 as a format used in the data link layer protocol.
(Point-to-Point Protocol) By using a frame (see FIG. 2) or the like, an IP datagram is placed in the data field of the frame or packet so that packet communication can be performed with the partner terminal.

In the example shown in FIG. 1, the transmission line between the terminal adapter 2 and the network adapter 4 is shown to be wirelessly connected, but the transmission line between the terminal adapter 2 and the network adapter 4 is connected by wire. It may be either in the case of using the wireless transmission line or in the case of using the wireless transmission line. For example, the configurations of the terminal adapter 2 and the network adapter 4 when using a wireless transmission path are shown in FIGS. 3 and 4.

As shown in FIG. 3, the terminal adapter 2
Has an attachment / detachment mechanism 31, an input / output device 32, a wireless transceiver 33, a wireless receiver 34, and antennas 35 and 36. The attachment / detachment mechanism 31 is for mechanically and electrically connecting the terminal adapter 2 itself and the terminal 1.
The input / output device 32 is connected to the terminal 1 via the attachment / detachment mechanism 31, and is also connected to the wireless transceiver 33 and the wireless receiver 34, and receives signals from the wireless receiver 34 or from the wireless transceiver 33. The reception signal is received and passed to the terminal 1 via the attachment / detachment mechanism 31, and the attachment / detachment mechanism 3
A signal received from the terminal 1 via the wireless transceiver 3
It is handed over to 3.

The radio transmitter / receiver 33 receives a signal transmitted through a narrow band transmission line (a signal transmitted at a low speed) via the antenna 35, demodulates it, and converts it into data. And has a low-speed wireless transmission / reception function of modulating data transmitted from the input / output device 32 and transmitting the modulated data via the antenna 35 through a low-speed wireless transmission path. In addition, the wireless receiver 34 receives a signal (high-speed transmitted signal) sent via a wide band transmission line from the antenna 3
It has a function of receiving the data via 6 and converting it into data, and passing it to the input / output device 32.

As shown in FIG. 4, the network adapter 4 includes a wired / wireless frame converter 41 and a wireless transceiver 42.
A wireless transmitter 43, a data link controller 44, a high-speed transmission line interface 45, and antennas 46 and 47.

The wire / wireless frame converter 41 is an ISDN.
The transmission frame from the (comprehensive service digital network) is converted into a wireless transmission frame, and the wireless transmission frame is converted into a wired transmission frame. For low-speed transmission, which receives and modulates the wireless transmission frame, wirelessly transmits it through the antenna 46, demodulates the wireless signal received through the antenna 46, and passes it to the wired / wireless frame conversion unit 41. Wireless transmitter and receiver.

The high-speed transmission line interface 45 is an interface for receiving transmission data from a high-speed communication network such as Ethernet, and the wireless transmitter 43 is a wideband for high-speed wireless transmission of a transmission frame based on the protocol control of the data link control unit 44. Is a high-speed wireless communication device.

The data link control unit 44 controls transmission / reception protocol in low-speed transmission and high-speed transmission communication, and the wired / wireless frame conversion unit 41 is based on the protocol control by the data link control unit 44. The frame to be transmitted is passed to the wireless transceiver 42, and the received frame is received. In addition, the wireless transmitter 43 is wired /
The transmission frame is retransmitted from the response frame received from the radio frame conversion unit 41 under the control of the data link control unit 44.

An advantage of using wireless transmission for communication between the terminal 1 and the network is that the mobility of the terminal 1 is improved. Therefore, even in LANs and public networks, wireless LANs that use wireless transmission for communication between the terminal 1 and the network 3, mobile phones, and the like have become widespread, and these terminals are compared with terminals that are connected by conventional wires. Then convenience is improved.

As shown in FIGS. 3 and 4, when the wireless transmission path is used for the communication between the terminal adapter 2 and the network adapter 4, the mobility of the terminal 1 can be similarly obtained. However, considering the usage pattern of the portable terminal 1, the information transmitted from the terminal 1 can be transmitted in the transmission band conventionally used for voice transmission, such as voice, keyboard input, and handwritten character input. The information received by the terminal 1 has a large capacity such as image information and the result of a database search, and a broadband transmission path is required to transmit such information without causing the user to feel stress.

In the terminal adapter 2 and the network adapter 4 using wireless transmission shown in FIGS. 3 and 4, the terminal 1 receives from the wireless carrier frequencies of the wireless transceivers 33 and 42 which transmit the data transmitted from the terminal 1. Wireless transmitter 43 and wireless receiver 3 for transmitting data to be transmitted
By increasing the radio carrier frequency of No. 4, it is possible to realize such an asymmetrical transmission line, and more than to realize a broadband transmission line for both transmission and reception by using a high frequency radio carrier. It can be said that this configuration is effective in terms of securing a power source for a mobile phone because a terminal adapter with low power consumption can be configured.

When the terminal 1 is a computer, its hardware configuration is basically the same as the configuration of a commonly used computer. The terminal adapter 2 is a computer internal bus or PCM which is an expansion hardware interface generally provided in a computer.
It is attached to the CIA interface.

Regarding the control function for controlling the packet communication, not only the method realized by hardware but also the function for inputting / outputting the signal exchanged with the above-mentioned terminal adapter 2 to / from a physical device such as a buffer capable of reading / writing from the CPU. According to the above, a method realized by software is possible. Here, without distinction of implementing the control method according to the present invention by hardware or software,
Its function and procedure will be mainly described.

The terminal 1 for implementing the packet communication control method according to the present invention, as shown in FIG. 5, for example, has a packet input unit 101, a control unit 102, a packet output unit 103, a timer unit 104, an input buffer 105, and an output buffer 106.
It is composed of

The packet input unit 101 checks the sequence number from the header of the received packet and determines whether the packet to be received has been received. If a correct packet is received, an instruction to generate a reception confirmation is issued.

The packet output unit 103 packetizes the data and transmits it, or transmits a reception confirmation packet based on an instruction to generate reception confirmation. In the timer unit 104,
For each packet that is sent, a resend timer is started at the time of sending to check whether the reception confirmation is received within the timeout time, measure the round trip time, and calculate the timeout time based on this measured round trip time. I do. The control unit 102 sets and releases a connection, which is a unit for data transmission, controls each connection, and manages a state.

Information such as the status of each connection is stored in the terminal 1
It is held in the memory of the terminal 1 through the above program. Further, the timer used in the timer unit 104 is calculated from the operation clock supplied to the CPU of the computer, and a plurality of timers corresponding to the accuracy are prepared, and each timer is selected and used according to the accuracy required for measurement or the like. To do. When transmitting data, the terminal 1 packetizes the data.

The packet has a header, a destination address as its additional control information to the tailor, its own address,
A sequence number indicating the sequence of data, an error detection code for detecting an error, and the like are written and transmitted.

In a communication system having such a basic configuration, as a first specific example of the present invention, even though all the transmission data is normally received by the receiving side, the data is transmitted from the receiving side to the transmitting side. Because the transmission of the confirmation response was delayed,
An example will be described in which it is possible to eliminate the waste of retransmitting the transmission data due to timeout on the transmission side.

(First Specific Example) In order to suppress retransmission of transmission data due to timeout at the transmitting side due to delay in acknowledgment, low-speed transmission is performed so that acknowledgment can be received before timeout. The transmission data may be appropriately divided and sent as a short packet.
In other words, after sending a packet from the data sending side, a confirmation response is returned from the receiving side to the data sending side, but the round trip time, that is, the data sending side confirms after sending the packet in the past. Based on the measurement value of the round trip time, which is the time required to receive a response, the timeout time of the retransmission timer used on the data transmission side (set for packet,
The data is divided and sent as multiple smaller packets so that the packet length is shorter than the time from sending the packet to the time-out) until the time required to reach the acknowledgment. To do so.

Since the packet length is shortened, the time required to transmit it can be shortened, and the sender can receive an acknowledgment before the sender times out.
It is possible to prevent occurrence of data retransmission without occurrence of timeout.

For that purpose, the structure of the packet output unit 103, which is a constituent element on the transmission side, may be devised so that it is as shown in FIG.

As a first specific example of the present invention, FIG. 6 shows a specific configuration example of the packet output unit 103 in the configuration of FIG. 5, which is a diagram showing a main part of the configuration on the terminal 1 side. That is, the data division processing unit 103a that divides the data to be transmitted in units of the amount of data calculated by a predetermined arithmetic expression corresponding to the transmission speed, etc., receives the data divided by the data division processing unit 103a, A packet output unit 103 of the terminal 1 is configured by a packet creation unit 103b that adds a header or a trailer to this and packetizes the packet.

With this configuration, when there is data to be transmitted on the terminal 1 side, this data is sent to the buffer 106 and stored there. Then, the packet output unit 103 on the terminal 1 side reads the data accumulated in the buffer 106, packetizes the data, and packet-transmits the data from the terminal 1 side to the other side through a low-speed transmission path. In the output unit 103, the data division processing unit 103a divides the data to be transmitted into a required length, and the packet creation unit 103b adds a header and a trailer to packetize the data and then transmits the packet to the other side.

In this example, the data division processing unit 1
The length of division at 03a is as follows. That is, the segment size (SS), which is the size of the data stored in one packet, is determined as follows.

Now, the currently set timeout time is RTO, the maximum segment size which is the maximum value of the data size stored in the packet is MSS, and the terminal 1
When the transmission rate of the data transmitted from V is defined as V, the segment size (SS) from these is set as SS + γ <min (MSS, RTO × V) (3) as shown in equation (3). At this time, γ is the time required to transmit the packet transmitted from the transmission side to the terminal 1 and received by the terminal 1. When the transmission rate of the data received by the terminal 1 is high, γ does not depend much on the packet length. It can be set to a constant value.

In the terminal 1, when the packet produced by the packet producing unit 103b is transmitted from the packet producing unit 103b through the low-speed transmission line, a command is given to the timer unit 104 to activate the retransmission timer for this packet.
It waits for the confirmation response from the other party to receive the packet-transmitted data without deleting it from the buffer 106.

When the receiving side receives and captures the packet, it returns a confirmation response. When the terminal 1 receives the confirmation response from the receiving side, the data in the buffer 106 is erased, When the confirmation response cannot be received, control is performed such that the confirmation response is saved without being erased for retransmission. The time to wait for the confirmation response is determined by the timeout time set in the retransmission timer of the timer unit 104 activated at the stage of transmitting the packet. That is, it is from the time when the packet is transmitted to the arrival point of a predetermined time.

When the confirmation response from the partner terminal cannot be received even after the time-out period has elapsed, the terminal 1
Will re-packetize and transmit the same data stored in the buffer 106 as the previously transmitted data.

When the timeout time is calculated according to the equation (1) or the equation (2), the timeout time is set to a relatively small value depending on the conditions.

For example, when the small packets are continuously transmitted from the terminal 1 and the variance of the sizes of these packets is small, the estimated value of the round trip time is calculated by the equation (1) or the equation (2). Is calculated to be small, and the timeout time is accordingly set to a relatively small value.

Therefore, when the maximum size packet including the maximum segment size data is transmitted during the control based on the timeout time shown in the formula (1) or the formula (2), the packet is transmitted to the partner terminal. The time required for transmission exceeds the timeout time.

Therefore, when there is a request to send a large amount of data, the data is divided into data of the size shown in equation (3) and then packetized and transmitted. In this case, since the size of the packet to be transmitted increases little by little, the measured value of the round trip time also gradually increases, and the estimated value of the round trip time described by the equation (1) or the equation (2) also increases. . Along with this, the set value of the timeout time also increases.

Therefore, when the data is divided as shown in the equation (3) and several packets are transmitted successively, eventually the timeout time shifts to a value at which the timeout does not occur even if the maximum size packet is transmitted. Do it.

Therefore, when the packet is transmitted from the terminal 1, the confirmation response packet cannot be received by the time-out time of the terminal 1 side even though the correct data is received by the other side. Since it is not judged as an error, it is possible to avoid unnecessary retransmission of the packet on the terminal 1 side, and it is possible to prevent unnecessary occupation of the transmission line due to unnecessary retransmission of the packet.

The packet transmitted from the partner terminal has the timeout time set by the formula (2) in the partner terminal. Since the transmission path for receiving the packet from the partner terminal has a wide band, the time required for the transmission is relatively short. Therefore, by packetizing the confirmation response together with the data shown in Expression (3) and transmitting the packet to the partner terminal, the partner terminal side does not wastefully time out.

Furthermore, while receiving data from the partner terminal at high speed and continuously, there is no occurrence of a congestion control procedure activated by a timeout on the partner terminal side, so packets can be received continuously. Therefore, the throughput can be improved.

As described above, in the case of connecting to a transmission line in which the transmission speed of the data transmitted from the terminal and the transmission speed of the data to be received by the terminal are greatly different from each other, for example, in the asymmetric communication method, The round trip time is affected by the packet transmission time on a narrow band transmission line with a low transmission rate, and is not so much dependent on the size of a packet transmitted on a wide band transmission line with a high transmission rate.

In practice, for example, when TCP / IP packets are transmitted using Ethernet, the ratio of the maximum IP packet to the minimum IP packet is "75: 2", although it depends on the measurement accuracy of the timer. In addition, the transmission rate of Ethernet is 10 Mbps, while the transmission rate of data transmitted from a terminal is, for example, P
When trying to communicate using HS (Personal Handyphone System), the transmission speed is 32 kbp.
In this case, the data transmission rate from the terminal is 32 kbps, and the data transmission rate of the data received by the terminal is 10 Mbps which is the Ethernet transmission rate. Therefore, the transmission rate ratio is " 2: 625 ".

Accordingly, the transmission time (transmission time) required for transmitting the minimum packet from this terminal to the other party and the time required for transmission (reception time) when the terminal receives the maximum packet from the other party Since the ratio is “25: 3”, the factor that occupies the round trip time at the terminal during normal packet transmission / reception is that the self-transmission time is longer than the time required for the other side to transmit the packet. It is considered that the ratio of the transmission time determined by the size of the packet to be transmitted is more decisive.

Therefore, in this specific example, the time element occupied by the confirmation response returned from the partner terminal side to the terminal 1 side is not changed, and the length of the packet of the data sent from the terminal 1 side to the partner terminal side is divided into data. By adjusting by processing, the length per packet is shortened so that the time until the acknowledgment is returned is allowed to be long and the timeout is prevented. Therefore, although data is correctly received, it is possible to suppress wasteful retransmission caused by delay in arrival of an acknowledgment and perform efficient data transmission.

An outline of the processing in the packet output unit 103 in the first concrete example is shown in FIG. In the processing here, the presence or absence of data input is checked (S10
1) If there is data input, the setting value of the segment size (SS) is updated based on the timeout time by the timeout time notification from the timer unit 104 (S1
02), it is checked whether or not the untransmitted data is larger than the set value (SS set value) (S103). As a result, when it is larger, only the set value (SS set value) is larger than the untransmitted data. The packet is taken out and a packet is created for this (S104, S105).

On the other hand, if the result of determination in S103 is not large, a packet is created for the untransmitted data (S105). Then, packet transmission processing (such as activation of a retransmission timer corresponding to the packet) is performed (S1
06), it is checked whether or not there is the next untransmitted data (S107).

Then, if there is untransmitted data, it is checked whether or not there is a retransmission instruction from the timer unit 104 (S1
08), if there is a retransmission instruction, the processing from step S105 is repeated, and if there is no retransmission instruction, step S102.
Repeat the process from.

Further, as a result of the judgment in step S107,
If there is no untransmitted data, it is checked whether or not there is a resend instruction (S109). As a result, if there is a resend instruction, the processing from step S105 is repeated, and if there is no resend instruction, the processing from step S101 is performed. Repeat.

As described above, the terminal 1 side appropriately divides the data to be transmitted by itself, packetizes each of the divided data, and transmits the packet as a short packet to the other side, thereby confirming the response from the other side. The example has been described in which the time that can be used for the transfer is secured and the time-out on the terminal 1 side can be avoided. This is to shorten the length of the transmission data on the data transmitting side and to improve the processing by giving it to the other side as a grace time for confirming the response, thereby avoiding the timeout on the terminal 1 side. It was an example.

However, even if the time-out on the side of the terminal 1 can be avoided, depending on the setting of the time-out time on the other side, a time-out may occur with respect to the data transmitted by the other side. Remain. And
Even if a time-out occurs on the other side, it is necessary to resend it, so it is necessary to improve this. Terminal 1
An example that is realized by the improvement of the processing in 1. will be described as a second specific example.

(Second Specific Example) The second specific example is the terminal 1
When the terminal receives data and returns its acknowledgment to the sender, the terminal 1 can control the sender so that it does not return the acknowledgment by embedding it in a large packet. This is an example in which a time-out on the side does not occur and retransmission is prevented, and efficient transmission is possible.

As described above, assuming the usage pattern of the portable terminal 1, since the terminal 1 is portable,
It is thought that the main thing is to move with the user and arbitrarily retrieve and use the information stored on the host side at the destination. In the future, considering the progress and spread of multimedia, that information will be received by the terminal 1. It is considered that there is a large amount of information about the data to be created. Considering the services provided to the terminal 1, it is considered that immediacy is often required, such as displaying the result of the database search on the terminal 1.

However, when the transmission path used for transmitting the confirmation response of the reception data used by the terminal 1 has a small transmission speed and a narrow band, the following problems occur. In other words, it does not matter much if the confirmation response is sent alone, but there are also cases where the confirmation response is embedded in the packet of the transmission data and transmitted, and the confirmation response is packetized and sent together with large data. This is a problem in the case of occurrence of such a situation. When such a situation occurs, it takes a long time for the terminal 1 to transmit the confirmation response to the received packet, and therefore the confirmation response from the terminal 1 should not arrive within the timeout time set by the other side. Happens.

Especially when trying to receive a large amount of data in a short time, the other party times out and congestion control is executed, so that it becomes impossible to receive a large number of packets in a short time. , The transmission efficiency drops sharply.

Therefore, in the second specific example, when the terminal 1 detects that it is receiving data, the terminal 1 is controlled so as not to transmit a large packet. FIG. 8 shows the configuration of the packet input unit 101, the control unit 102, and the packet output unit 103 of the terminal 1 according to the second specific example of the present invention that can perform such control.

The packet input unit 101 is the packet decomposition unit 1.
01a and the sequence number confirmation function unit 101b, the control unit 1
02 has a function of a confirmation response transmission waiting flag and a notification function during burst reception to the data division processing unit 103a, and the packet output unit 103 has a data division processing unit 103a.
And a packet creation unit 103b.

The data division processing unit 103a is a functional unit which, when receiving the notification during burst reception, divides the data to be transmitted in units of data amount calculated by a predetermined arithmetic expression corresponding to the transmission speed and the like. The packet creation unit 103b is a functional unit that receives the data divided by the data division processing unit 103a, adds a header and a trailer to the data, packetizes the data, and sends the packet to the transmission path.

Further, the packet disassembling unit 101a disassembles the packet received from the transmission path into necessary information, sends it to the input buffer 105, and outputs the sequence number of the data contained in the packet and the sequence number of the acknowledgment. It has a function of giving the sequence number confirmation function unit 101b.

The sequence number confirmation function unit 101b confirms these sequence numbers, resets the retransmission timer corresponding to the acknowledged packet in the timer 104, and
It has a function of giving a command to the control unit 102 in order to set a confirmation response transmission waiting flag corresponding to a received packet.

The timer 104 has a plurality of retransmit timers, and manages the time-out by performing start-up and reset by managing in accordance with the packet.

Further, the control unit 102 receives the command for setting the confirmation response transmission waiting flag corresponding to the received packet, sets the flag, and passes the information of the confirmation response of the packet to the packet creation unit 103b. Further, it is confirmed whether or not the burst reception is being performed, and when the burst reception is being performed, a function of giving a burst reception notification to the data division processing unit 103a, and
It has a function of resetting the acknowledgment transmission waiting flag in accordance with an instruction from the packet creation unit 103b.

In this device (terminal 1), when a packet is received from the other party via the transmission line, the packet input unit 101
Then, the packet decomposing unit 101a decomposes the packet and sends it to the input buffer 105, and the application takes in the data in the input buffer 105 and performs the required processing. The information of the data sequence number, the confirmation response, and the sequence number included in the header decomposed by the packet disassembly unit 101a is sent to the sequence number verification function unit 101b.
The timer 104 for the packet acknowledged here
Stop the timer by issuing a command to reset the resend timer.

Further, the sequence number confirmation unit 101b sends a command for setting a confirmation response waiting flag corresponding to the sequence number of the received packet to the control unit 102, and the control unit 102 waits for the confirmation response transmission of the corresponding packet by this command. Set the flag. When it is determined that the burst reception is in progress, a burst reception notification is sent to the data division processing unit 103a.
Give to.

When there is data in the output buffer 106, the data division processing unit 103a takes in this data, and when the data amount is large, divides it into a predetermined data length range and gives it to the packet creation unit 103b. Here, after packetizing this data, it is transmitted to the other party via the transmission path.

In transmitting the acknowledgment information, if another data to be transmitted to the other party exists in the output buffer 106, the acknowledgment information is also stored in the same packet together with the other data and transmitted. However, when packets are continuously received from the other party, the data is divided within a range that fits into a short packet length according to a predetermined arithmetic expression, and it is packetized with the information of the acknowledgment and sent to the other party. .

Of course, at this time, the information of the confirmation response may be individually packetized and transmitted to the other party.

The fact that the terminal 1 is receiving data is detected by the confirmation response transmission waiting flag. For example, in the case where the method in which the reception confirmation is sent in packetized form together with the normal data is adopted, the terminal 1 does not immediately send the reception confirmation immediately after receiving the packet, but the data to be transmitted to other data. Wait for

Therefore, when the terminal 1 receives the packet, as described above, the flag indicating the transmission waiting state of the confirmation response is set. Then, the packet output unit 1
When this flag is set, 03 recognizes that it is receiving with this flag, and upon detection of this flag, returns a reception confirmation for the packet for which the flag is set to the other party.
At this time, if there is other data to be sent to the other party, in a normal state, the reception confirmation is packetized together with these data and transmitted to the other party.

However, when packets are continuously received from the other party, the confirmation response is packetized to a data length within a predetermined short packet length, or the confirmation response is individually packetized and returned to the other party. To

In order to detect that the terminal 1 is receiving a large amount of data in a burst, the control unit 102 records, for example, the time when the packet containing the data is received, and records this record. Calculate the reception time interval based on
This can be realized by detecting when this exceeds a predetermined threshold value.

The procedure for performing such processing is shown in FIG. FIG. 9 is a flowchart showing a processing procedure in the packet output unit 103 in the configuration of FIG. 8, and the processing here checks whether or not there is data input (S20).
1) If there is a data input, then it is checked whether or not there is a burst reception notification (S202). As a result, if there is a burst reception notification, the set value of the segment size (SS) is reduced (S203). . The set value of the segment size (SS) in that case is based on Formula (4). Then, it is determined whether or not the untransmitted data is larger than the set value (set value of SS) (S205).

On the other hand, as a result of the judgment in step S202,
If there is no notification during burst reception, the segment size (S
The set value of S) is set to the maximum value (S204). Then, it is determined whether or not the untransmitted data is larger than the set value (set value of SS) (S205). If the result of determination in step S205 is that the untransmitted data is larger than the set value (set value of SS), data of the SS set value is extracted from the untransmitted data, and a packet is created for this. Perform (S206, S207).

Further, as a result of the judgment in step S205,
If the untransmitted data is smaller than the set value (set value of SS), all the untransmitted data is taken out and a packet is created for this (S207).

Then, packet transmission processing (such as activation of a retransmission timer corresponding to the packet) is performed (S20
8) It is checked whether or not there is next untransmitted data (S
209).

Then, if there is untransmitted data, it is checked whether or not there is a retransmission instruction from the timer unit 104 (S2
10) If there is a retransmission instruction, repeat the processing from step S207, and if there is no retransmission instruction, step S202.
Repeat the process from.

Further, as a result of the judgment in step S209,
If there is no untransmitted data, it is checked whether or not there is a resend instruction (S211). As a result, if there is a resend instruction, the processing from step S209 is repeated, and if there is no resend instruction, the processing from step S202 is performed. I repeat.

As described above, when it is detected that packets containing a large amount of data are continuously received, when an acknowledgment is returned to the received packet, the data is divided into smaller sizes and confirmed. Priority is given to the transmission of the acknowledgment, such as packetizing with the response or making it a packet only for the acknowledgment, so that it will not be returned in a large packet that includes the acknowledgment with other large transmission data. Therefore, the confirmation response can be returned to the other party in a short time.

In this case, the segment size (SS) when packetizing the data is set as shown in equation (4).

SS <δ (4) Here, δ is determined by the size of the packet that can be sent in a time that does not cause a timeout on the other side. For example, on a transmission line in which the minimum packet length is defined, the data that can be included in the packet is δ. Alternatively, in a protocol in which the minimum value of the timeout time is defined, the size of the packet that can be sent within that time is δ.

By using this method, at least when the terminal 1 is receiving data in a burst, these acknowledgments can be delivered to the other side without exceeding the time-out time. It is possible to eliminate the problem that a timeout occurs even though the correct data is received. Therefore, it is possible to shorten the reception time when receiving data in bursts.

As described above, when the amount of data received from the other party is large, the confirmation response to the packet may be the confirmation response alone or may be packetized together with other data within the range of a packet of a predetermined small size. In this example, the confirmation response is returned in time for the other party's timeout time so that the other party's retransmission is eliminated.

Next, when the data transmission source is the terminal 1, when the terminal 1 transmits a packet L larger than a predetermined size to the other party, the confirmation response from the receiving party is delayed by that amount. An example in which the timeout of the terminal 1 of the transmission source is suppressed by the following will be described as a third specific example.

(Third Concrete Example) When the terminal 1 transmits a packet L larger than a predetermined size, the acknowledgment from the receiving party will be delayed by that amount.
An example in which the optimum timeout time is set so that the terminal 1 of the transmission source does not time out due to the delay will be described as a third specific example.

When the terminal 1 is used as a reference, the packet output for suppressing the retransmission of the packet transmitted from the terminal 1 to the partner terminal due to the fact that the acknowledgment from the partner terminal cannot be received by the timeout time. The configuration of the unit 103 is shown in FIG.

As shown in FIG. 10, in this example, the packet output unit 103 comprises a data division processing unit 103a and a packet creation unit 103b, and the data division processing unit 103a fetches transmission data from the output buffer 106 and divides the data. At the same time, it has a function of notifying the timer unit 104 of the packet length obtained when a packet is created from the divided data. Further, the packet creation unit 103b has a function of packetizing the data received from the data division processing unit 103a and sending it to the transmission path, and when sending a packet to the packet creation unit 103b, it starts a retransmission timer corresponding to the packet. As described above, when a command is issued to the timer unit 104, and the timer unit 104 issues a retransmission instruction for a packet corresponding to the retransmission timer for which the timeout has occurred, the instruction is received. It has a function of retransmitting the corresponding packet.

FIG. 11 shows a configuration example of the timer section 104. The timer unit 104 includes a round trip time measuring unit 104a, a timeout time calculating unit 104b, a timer managing unit 104c, and a plurality of retransmission timers 104d.

The round trip time measuring unit 104a sends the packet from the packet output unit 103 to the transmission line, and the time until the packet of the confirmation response to the packet is obtained from the packet input unit 101 is calculated by the packet output unit 103, the packet The measurement is performed using the information from the input unit 101, and the timeout time calculation unit 104b
Is a functional unit that obtains a timeout time according to a predetermined calculation formula based on this measurement information and packet length notification information. If the measurement time and packet length are within a predetermined standard value, the standard value is supported. The optimum predetermined timeout time that has been set is output, and among the plurality of retransmission timers 104d,
It has a function of setting the packet-based retransmission timer 104d and activating it.

Each retransmission timer 104d is a functional section for counting time, and has a function of outputting timeout information when the set timeout time is reached. In addition, the timer management unit 104c uses the plurality of retransmission timers 1
Of 04d, retransmission timer 104d that has timed out
Then, it has a function of determining which packet needs to be retransmitted from the timeout information and instructing the packet output unit 103 to retransmit the packet.

In such a configuration, the output buffer 1
When there is data to be transmitted in 06, the data division processing unit 103a takes in this data, divides it into a range within a predetermined packet length, and divides this into a packet generation unit 10
3b, packetize this data here, and transmit it to the other party via the transmission path.

On the other hand, the packet length of the packet to be transmitted is notified to the timer unit 104, and the timer unit 104 uses the value added with the time required for transmission of the packet as the formal timeout time (RTOl) for the packet. Set the retransmission timer to use for retransmission management.

Therefore, the reference length of the packet to be transmitted is set in advance, and if the packet to be transmitted is within the range of this reference length, the standard timeout time calculated by the equation (1) or the equation (2) is set. If a retransmission timer is set for the packet and used for retransmission management, and the packet to be transmitted is larger than the reference length, the value required to add the time required to transmit the packet to the standard timeout time will be the official timeout. The time (RTO1) is set in the retransmission timer for the packet and used for retransmission management.

Therefore, when the transmission packet is within the defined length, the retransmission control can be managed with the standard timeout time, and when the transmission packet is longer than the defined length, it becomes longer. It becomes possible to manage the retransmission control by increasing the timeout time by the amount of time, and it is possible to prevent frequent retransmissions due to timeouts. Also, if the packet is within the standard length, the standard timeout time You can manage retransmission control with
For a relatively short packet, retransmission control can be performed with a short optimal timeout time, and for a long packet, retransmission control can be performed with an optimal timeout time accordingly.

That is, according to the present invention, when the terminal 1 transmits a packet L larger than a predetermined size, the timeout time calculated from the equation (1) or the like
Basically, a value added with the time required to transmit the packet is set as a formal timeout time (RTOl) for use.

At this time, the official timeout time (RTO
l) is calculated as RTOl = RTO + L / V (5) as shown in equation (5).

Further, from the measured value of the round trip time in the equation (1), the time required for transmitting the packet transmitted from the terminal 1 in the measurement is subtracted, and the terminal 1
Alternatively, a method of calculating the timeout time by using the equation (5) when the packet is transmitted from That is, when the size of the packet transmitted at the time of measuring the round trip time is M, it becomes as shown in Expression (6).

RTT = αRTTpre + (1−α) (RTTovs −M / V) (6) Further, the time-out time (RT
O) is calculated.

According to the above-mentioned method, a situation occurs in which the packet transmitted from the terminal 1 is retransmitted unnecessarily even though the other terminal receives correct data. Since it is eliminated, a narrow band transmission line can be effectively used.

Next, a specific example will be described as a fourth specific example, which addresses the problem of how to set the optimum timeout time for efficient transmission in the case of transmission on a high quality transmission line.

(Fourth Concrete Example) When there are few errors on the transmission line or when error correction is performed by the transmission line coding, the packet being transmitted on the transmission line is added to the data or header part of the packet. Since there are few mistakes,
Because the correct data did not reach the other terminal,
It is considered that there are few cases where the confirmation response cannot be received.

Therefore, when there are few errors in the transmission path, throughput is less deteriorated even if the timeout time is set to a large value. Therefore, it is not necessary to adaptively control the detailed value of the timeout time, but the maximum value is set beforehand. An effective method is to measure or estimate the transmission time when a packet is transmitted, and set the timeout time so that it does not become shorter than that time.

The formula used for the timeout time setting calculation at this time is shown in formula (7). Here, ε is a constant value or a statistically-estimable estimated value that takes into account fluctuations in transmission time when the maximum packet is transmitted due to fluctuations in processing at the terminal.

If (RTO ≦ MSS / V + ε) then RTO = MSS / V + ε (7) That is, the timeout time “RTO” is “MSS / V”.
When less than or equal to + ε, "RTO" is "MS
S / V + ε ″.

According to the present invention, when there are few errors on the transmission line or when error correction is performed by the transmission line coding, the terminal does not need to perform adaptive control with respect to the detailed value of the timeout time. In either case, the packet that was sent or received by the terminal will not be retransmitted unnecessarily when the packet is received correctly. Therefore, it is possible to improve throughput and receive bursty data in a short time. It can be carried out.

Although various concrete examples have been described above, the present invention is, in short, communication using a transmission line in which the transmission speed of the transmission data to the terminal is higher than the transmission speed of the transmission data from the terminal. In the system, the data to be transmitted is packetized, and when a packet is received, an acknowledgment is returned, and when a packet is sent, the retransmission timer starts timing, and an acknowledgment is sent from the receiving side by the lapse of a predetermined timeout time. If there is no, in the packet communication system that tries to retransmit the packet, within the timeout time of the retransmission timer determined from the measured value of the round trip time required from transmitting each packet to receiving the acknowledgment, The packet length of the packet to be transmitted is shortened so that the acknowledgment can be received. To this end, if the data length to be transmitted is long, the packet length is shortened by dividing and packetizing, and if the acknowledgment is packetized and sent together with other data, whether the other data is divided or not. Alternatively, only the acknowledgment is packetized so that the acknowledgment can be received within the timeout time of the retransmission timer.

Therefore, it is possible to eliminate the waste of retransmitting the packet on the transmitting side because the confirmation response is delayed in spite of the normal reception of the packet, which hinders the continuous transmission of the packet due to the occurrence of timeout. Through this, it is possible to eliminate the decrease in throughput due to the above, and to suppress the waste of communication resources.

Further, the timeout time of the retransmission timer is made variable according to the length of the packet to be transmitted, and this also causes the retransmission of the packet to be retransmitted on the transmitting side because the acknowledgment is not in time even if the packet is normally received. By doing so, it is possible to eliminate the waste of performing the processing, and it is possible to solve the decrease in throughput due to the interruption of the continuous transmission of packets due to the occurrence of timeout, and it is possible to suppress the waste of communication resources.

The present invention is not limited to the above-mentioned specific examples, and can be variously modified and implemented.

[0147]

As described in detail above, according to the present invention,
Even though packets are normally received, the acknowledgment does not arrive in time, so it is possible to eliminate the waste of retransmitting packets on the transmitting side, and throughput due to interruption of continuous packet transmission due to timeout. It is possible to solve the problem of being able to eliminate the decrease of the communication resource and to suppress the waste of communication resources.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration example of a system of the present invention for explaining the present invention.

FIG. 2 is a diagram for explaining the present invention, in which PPP (P
The figure which shows the structural example of an oint-to-point protocol) frame.

FIG. 3 is a diagram for explaining the present invention and is a diagram showing a configuration example of a terminal adapter 2 when a wireless transmission path is used.

FIG. 4 is a diagram for explaining the present invention and is a schematic block diagram showing a configuration example of a network adapter 4 when a wireless transmission path is used.

5 is a diagram for explaining the present invention and is a schematic block diagram showing a configuration example of a terminal 1. FIG.

FIG. 6 is a diagram for explaining the present invention and is a diagram showing a configuration example of a packet output unit 103 in the first specific example of the present invention.

FIG. 7 is a diagram for explaining the present invention and is a diagram showing an outline of processing in the packet output unit 103 in the first specific example of the present invention.

FIG. 8 is a diagram for explaining the present invention, which is a packet input unit 101 of the terminal 1 in the second specific example of the present invention;
The figure which shows the structure of the control part 102 and the packet output part 103.

9 is a diagram for explaining the present invention and is a flowchart showing a processing procedure in the packet output unit 103 in the configuration of FIG.

FIG. 10 is a diagram for explaining the present invention and is a diagram showing a configuration example of a packet output unit 103 in the third specific example of the present invention.

FIG. 11 is a diagram for explaining the present invention and is a diagram showing a configuration example of a timer unit 104 in the third specific example of the present invention.

FIG. 12 is a diagram showing the structure of a packet of an IP (Internet Protocol) datagram.

FIG. 13 is a diagram showing a configuration example of a TCP packet.

FIG. 14 is an operation transition diagram showing an example of a communication procedure in communication using TCP, and FIG. 14A shows an example in which an acknowledgment can be received within a timeout time after self packetizing and transmitting the data. FIG. 7B is a diagram showing an example of packet re-transmission and a timeout that occurs when a packet is lost.

[Explanation of symbols]

 1 ... Terminal 2 ... Terminal adapter 3 ... Network 4 ... Network adapter 31 ... Detachment mechanism 32 ... Input / output device 33 ... Wireless transceiver 34 ... Wireless receiver 35,36 ... Antenna 41 ... Wired / wireless frame converter 42 ... Wireless transmission / reception Device 43 ... Wireless transmitter 44 ... Data link control unit 45 ... High-speed transmission line interface 46, 47 ... Antenna 101 ... Packet input unit 102 ... Control unit 103 ... Packet output unit 103a ... Data division processing unit 103b ... Packet creation unit 104 ... Timer unit 105 ... Input buffer 106 ... Output buffer

Claims (7)

[Claims] 1. The transmission rate of data to be received by a terminal is
A communication system that uses a transmission path that is faster than the transmission speed of data sent from a terminal, and transmits data exchanged with the terminal in packets, and returns an acknowledgment when a packet is received. In addition, when a packet is transmitted, the retransmission timer starts timing, and if there is no acknowledgment from the receiving side before the elapse of a predetermined timeout time, the packet transmission system tries to retransmit the packet. The time required for transmission of packets transmitted by this terminal is shorter than the timeout time of the retransmission timer, which is sequentially calculated from the measured value of the round trip time required from transmitting each packet to receiving the acknowledgment. A packet communication system characterized by comprising packet output means for dividing data into packets and packetizing them. Stem. 2. The transmission rate of data to be received by the terminal is
A communication system that uses a transmission path that is faster than the transmission speed of data sent from a terminal, and transmits data exchanged with the terminal in packets, and returns an acknowledgment when a packet is received. In addition, when a packet is transmitted, the retransmission timer starts counting, and if there is no acknowledgment from the receiving side before the elapse of a predetermined timeout time, it attempts to retransmit the packet. When the self receives the packet and is in the waiting state for sending the acknowledgment, the time required for transmitting the packet sent by the self becomes shorter than the predetermined time,
A packet communication system having a function of dividing data into packets. 3. The transmission rate of data to be received by the terminal is
A communication system that uses a transmission path that is faster than the transmission speed of data sent from a terminal, and transmits data exchanged with the terminal in packets, and returns an acknowledgment when a packet is received. In addition, in the packet communication system, when the packet is transmitted, the retransmission timer starts counting, and if there is no acknowledgment from the receiving side by the elapse of a predetermined timeout time, the packet is retransmitted. It has a function to determine the timeout time of the retransmission timer for the packet to be transmitted next based on the measured value of the round trip time from transmitting the packet to receiving the acknowledgment and the size of the packet to be transmitted next. A characteristic packet communication system. 4. The transmission rate of data to be received by the terminal is
A communication system that uses a transmission path that is faster than the transmission speed of data sent from a terminal, and transmits data exchanged with the terminal in packets, and returns an acknowledgment when a packet is received. In addition, in the packet communication system, when the packet is transmitted, the retransmission timer starts counting, and if there is no acknowledgment from the receiving side by the elapse of a predetermined timeout time, the packet is retransmitted. A function that determines the timeout time of the next packet to be transmitted based on the measured round trip time from the transmission of a packet to the receipt of an acknowledgment and the time required to transmit the maximum packet that the terminal can transmit A packet communication system comprising: 5. The transmission rate of data to be received by the terminal is
A communication system that uses a transmission path that is faster than the transmission speed of data sent from a terminal, and transmits data exchanged with the terminal in packets, and returns an acknowledgment when a packet is received. In addition, when a packet is transmitted, the retransmission timer starts timing, and if there is no acknowledgment from the receiving side before the elapse of a predetermined timeout time, packet transmission is attempted in a packet communication system. It outputs data in packets, and based on the given timeout time information, divides the data into packets to optimize the transmission packet length, packetizes them, and sends them to the transmission path. The packet receiver that receives the packet and the round trip from the time the packet is sent until the acknowledgment is received. Retransmission timer function that measures the timeout time, determines the timeout time based on this round trip time, gives the timeout information to the packet transmitter, and measures the time elapsed after transmitting each packet. And a timer unit having: 6. The transmission rate of data to be received by the terminal is
A communication system that uses a transmission path that is faster than the transmission speed of data sent from a terminal, and transmits data exchanged with the terminal in packets, and returns an acknowledgment when a packet is received. In addition, when a packet is transmitted, the retransmission timer starts timing, and if there is no acknowledgment from the receiving side before the elapse of a predetermined timeout time, the packet transmission system tries to retransmit the packet. A packet transmission unit that packetizes and transmits to the transmission line, a packet reception unit that receives packets from the transmission line, multiple retransmission timers that measure the time elapsed after each packet transmission, and packet transmission The round trip time and the packet length. Packet communication system characterized by comprising: a means for determining the time-out time and. 7. A communication system using a transmission line in which the transmission speed of data sent to a terminal is higher than the transmission speed of data sent from the terminal, and the data to be transmitted is packetized and packets are received. Packet communication that attempts to retransmit the packet, and when the packet is sent, attempts to retransmit the packet by starting the time measurement of the resend timer and if there is no acknowledgment from the receiving side before the elapse of a predetermined timeout time. In the system, shorten the packet length of the packet to be transmitted so that the acknowledgment can be received within the timeout period of the retransmission timer, which is determined by the measurement value of the round trip time required for sending each packet until receiving the acknowledgment. A packet communication control method characterized by the above.