JPH114225A - Data transmitter and data transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dynamically control the transmission band of high band burst traffic in accordance with the increase of use band of other traffics by providing a means for controlling the transmission band with a transmission station and deciding a new transmission band of the transmission station which transmits a data packet at a reception station based on the result of connection detection means. SOLUTION: A transmission band control means 1 at a transmission station controls a start of data transmission and a band change or the like of data transmission in accordance with a transmission instruction informed by a reception station. The reception station receives a packet traffic which makes a wide band burst traffic and a narrow band traffic multiplexed on the same transmission channel, a band for use measuring means 2 measures the total band for use by these packet traffics and a connection detection means 3 detects a connection message switching. A transmission band decision means 4 decides and instructs an initial value of the transmission band of the wide band burst traffic based on the measured result of the use band.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a packet switching network for multiplexing packets from a plurality of transmitting stations on the same transmission channel and transmitting the multiplexed packets to a receiving station. The present invention relates to a data transmission apparatus and a data transmission method for avoiding congestion in the above.

[0002]

[Prior art]

[Transmission Bandwidth Contention] When a plurality of terminals perform data transmission at an arbitrary timing on the same network, transmission bandwidth contention occurs between the transmissions. The network has
Generally, a plurality of terminals are connected, and data transmission is performed between the terminals via transmission media constituting a network. The transmission band is represented by the amount of transmission data per unit time.
The transmission capacity of the transmission medium is limited, and its maximum transmission band Rmax is a fixed and finite value.

[0003] The bandwidth of a transmission medium is shared by a plurality of data transmissions, and each data transmission uses a band according to the amount of transmission data per unit time. The bandwidth usage r (t) of each data transmission changes every moment.

[0004] If the total bandwidth usage 使用 r (t) of the data transmission sharing the bandwidth of the same transmission medium is larger than the maximum transmission bandwidth Rmax of the transmission medium, the contention of the shared bandwidth between the respective data transmissions may occur. Become. This is called a conflict.

[0005] Contention occurs for the following reasons. The subject of data transmission is an application running on each terminal connected to the network. Generally, multiple types of applications run on a terminal. Also, of course,
Multiple applications run on the entire network. The status of data transmission by each application includes the start time, end time, transmitting terminal, receiving terminal,
It is characterized by the change over time of the route and the band used. Some applications that perform data transmission include, for example, t
Some applications, such as elnet, have unpredictable data transmission conditions.

[0006] On the other hand, data transmission is generally realized by a functional hierarchical structure typified by the seven-layer reference model of the ISO. In a function hierarchy that controls transmission, information that can be obtained only by a specific application cannot be premised on control. In other words, when viewed from the side of the transmission medium that is functionally lower than the application, the status of data transmission from each application that performs data sharing by sharing it is all treated as unobtainable information. .

Therefore, in a conventional network,
It is difficult to keep track of all transmission conditions such as the start time and end time of each data transmission, the transmission terminal, the reception terminal, the route, and the change in the bandwidth used, and such information is statistically and stochastically predicted. Was common.

An application that performs data transmission on a network generally operates independently, and each application that does not execute the avoidance-type congestion control, which will be described later, operates independently of the state of data transmission by other applications. Perform data transmission. Therefore, each data transmission is independent of each other, and is controlled plurally at each transmitting end.

In such a situation, focusing on one data transmission, the available bandwidth R
(T) changes from moment to moment in consideration of the state of band use of other data transmission. Other data transmissions are controlled independently at each transmitting end. Therefore, it is impossible for the transmitting end of the data transmission to grasp the band usage status of the other data transmission.

[0010] At the transmitting end of data transmission, when the band usage of other data transmission is predicted and the amount of band used by its own data transmission is controlled, if the prediction is erroneous, the same transmission medium is shared. In some cases, the sum 帯 域 r (t) of the data transmission band usage exceeds the maximum transmission band Rmax of the transmission medium.

It is desirable to avoid such competition because it reduces the efficiency of band use. In other words, if the band required for transmission cannot be obtained due to band contention,
That much data is lost. Generally, when data is lost, the data is retransmitted, but this reduces the effective bandwidth utilization efficiency [the amount of data successfully transmitted / the amount of bandwidth used for transmission]. In order to suppress contention and efficiently utilize the maximum transmission bandwidth of the limited transmission medium, the transmission end of the data transmission determines the bandwidth R (t) available for the transmission at that time and the transmission. Band used r (t)
Need to be controlled equally.

[Conventional Band Contention Control System] Next, a conventional band contention control system in a conventional transmission technique will be described. In order to perform a plurality of data transmissions by sharing the same transmission medium, an exchange technique for allocating a band between the data transmissions is required. A typical switching technique is a packet switching scheme. In this method, data is divided into small units called packets and transmitted. A packet is allocated a band each time it reaches each transmission medium on its transmission path. In other words, in packet switching, the bandwidth of each transmission medium is dynamically allocated in packet units between data transmissions sharing the bandwidth at each time.

As a control method of band contention in this packet switching system, there is an additional value control. This is because, for a fluctuating target value [bandwidth R (t) available for transmission at time t], control amount [bandwidth r used for transmission at time t]
(T)] to calculate the difference | R (t) −r (t) |
Is controlled to be zero.

In the packet switching system, the bandwidth is dynamically allocated to the transmission actually using the bandwidth of the transmission medium, so that the maximum transmission bandwidth Rmax of the transmission medium can be used without waste. However, on the other hand, it is necessary to perform additional value control of the used band, and in that case, there may be an excess or deficiency in the operation of the control amount.

For example, when R (t) -r (t)> 0 (control amount is insufficient), a band not used for transmission occurs,
Band utilization efficiency decreases.

If R (t) -r (t) <0 (excess control amount), the transmission bands compete. In general, excessive buffering is absorbed by buffering data before and after the transmission medium and averaging the bandwidth usage over time. However, buffers are also subject to contention, as are bandwidths. Further, even when the buffer length is sufficiently long, data transmission delay due to buffering increases. In general, the data transmission delay increases in accordance with the increase of the band contention, and accordingly, the variation of the data transmission delay also increases.

As shown in FIG. 1, in a packet switching network in which a plurality of transmitting stations transmit data to the same receiving station at an arbitrary timing, a packet transmitted from each transmitting station is transmitted to the receiving station. In a buffer to be multiplexed on a channel (hereinafter referred to as a multiplexing buffer), a state in which the sum of the used bandwidth of the input packet traffic (the input bandwidth to the buffer) exceeds the transmission channel bandwidth (the output from the buffer) occurs. There is.

In such a case, the input packets exceeding the transmission channel band stay in the multiplexing buffer and wait for an output opportunity. However, since the buffer amount is limited, the packets are lost due to the buffer overflow. Has danger. Loss of a packet results in a transmission error, which in turn causes a reduction in band use efficiency due to retransmission. This state is called congestion.

[Conventional congestion control method] In order to avoid congestion or to recover from congestion, it is necessary to control the transmission band at the transmitting station and suppress input to the multiplexing buffer. This is called congestion control. The congestion control method includes A.I. A recovery-type congestion control scheme; There is an avoidance type congestion control method.

A. Recovery type congestion control method As described above, it is impossible to accurately predict a change in a target value in performing additional value control of a used band. Therefore, as a congestion control method conventionally performed in packet switching, there is a recovery type congestion control method, so-called feedback control (also called closed loop control).

The recovery-type congestion control method uses the following method during data transmission.
Each transmitting station independently and autonomously controls the transmission band according to the observed value of the congestion result event (buffer retention amount or packet loss).

Therefore, each transmitting station can start data transmission at an arbitrary timing without delay. However, on the other hand, the period from when the occurrence of the congestion state or when the transition to the congestion state is detected to when the congestion state is released by the transmission bandwidth control according to the detection includes a round-trip delay proportional to the distance. Therefore, buffer overflow due to control delay is inevitable in principle.

The recovery type congestion control method is applied under the following conditions.

1. Round trip delay is short,
The used band of each multiplexed traffic is relatively narrow with respect to the band of the transmission channel, and the effect of the fluctuation can be absorbed by the multiplexing buffer.

2. In the transmission request, packet loss is allowed. That is, even if a packet is lost, delay due to retransmission does not matter or retransmission is not necessary.

In the recovery type congestion control, the difference between the target value and the control amount at the observation point is observed and returned to the control point as feedback information. At the control point, the control amount is operated based on the information. The additional value control of the used band using feedback largely depends on the observation point of the feedback information. b. Is divided into two.

A. A technique for observing the usage status of a shared band in a transmission medium sharing a band and feeding back the result to a transmitting end. A typical technique actually applied is Ether
net, CSMA / CD scheme, CI scheme using rm cell in ATM ABR service, and E
There are the R method and the like. CSMA / CD: Carrier Sense Mul
single Access with Collisi
on Detection ATM: Asynchronous Transfer
Mode ABR: Available Bit Rate rm: Resource Management CI: Congestion Indication ER: Explicit Rate

B. The data receiving end detects the data loss and feeds back the result to the transmitting end, and the data transmitting end regards the data loss as a result of the band contention. As a typical technique actually applied, there is a slow start method in TCP. TCP: Transmission Control
Protocol

The following a. In the transmission medium sharing the band, a specific example of a method of observing the usage status of the shared band and feeding back the result to the transmitting end will be described.

A-1. The CSMA / CD system Ethernet is a bus-type passive physical transmission medium and can transmit a single packet (referred to as a frame in Ethernet) at the same time. Therefore, distributed contention control at each transmitting end in frame units. I do.

The transmitting end of the frame monitors the signal on the transmission medium (Carrier Sense) and detects the transmission status of another frame. If there are no other frames on the transmission medium, send its own frame,
Therefore, when a plurality of terminals transmit frames at the same time, a collision of frames occurs.

At each transmitting end, upon detecting a frame collision, transmission is interrupted, and the Binary Expone is transmitted.
The period during which the collision probability is expected to be low is determined by the neutral Backoff algorithm, and after that period, the frame transmission is attempted again.

A-2. rm cell CI system (ATM
-ABR) In ATM, an active full-duplex (upward / downward bidirectional communication) transmission medium called a packet (called a cell in ATM) switch is used. In the cell exchange, cells transmitted from each terminal are temporarily buffered and transmitted (switched) to respective destination paths. For this reason, the transmission end can control the amount of use of the transmission band by controlling the cell transmission interval.

In the ATM, the switching within the exchange and the congestion of the transmission band at the cell switching destination (Co
Negation) may occur. The rm cell is transmitted from each transmitting end at regular intervals, passes through an exchange on a data transfer path, and is returned to the transmitting end when it reaches the receiving end.
In the CI system, when congestion is detected in an exchange on a data transfer path, the occurrence of congestion is notified to the transmitting end using an rm cell passing through the exchange at that time.
At the transmitting end, when the occurrence of congestion is detected by the rm cell, the used band is reduced to the band usage expected to be able to stochastically avoid congestion, and when the notification of the congestion by the rm cell is released, The bandwidth used gradually increases.
Even when data transfer is performed after a pause for a certain period or more, the bandwidth usage gradually increases from a low bandwidth usage expected to not cause congestion.

A-3. ER system using rm cell (ATM
-ABR) In the ER system, when congestion is detected in the exchange on the data transfer path, the exchange uses the rm cell passing through the exchange at that time to estimate the amount of band usage expected to avoid congestion from the exchange. Notify the sending end. At the transmitting end, when the use band is specified by the rm cell, the use band is operated based on the instruction.

In addition, b. Data loss is detected at the data receiving end, the result is fed back to the transmitting end, and the data transmitting end considers the data loss as a result of band contention. There is.

B-1. Slow Start method (TC
P) TCP is a transport protocol that guarantees the reliability of data transfer. In standard TCP, the receiving end of the data only informs the transmitting end that the data has been received. The detection of data loss is indirectly detected when the notification of data reception from the receiving end times out. When the data transmitting end detects a data loss, it retransmits the data to the receiving end.
In the SlowStart method, when a data transmission end detects a data loss, it is regarded as having occurred as a result of band contention and the data transmission interval is adjusted.

Specifically, the data to be continuously transmitted is only one packet. When the reception of the data is confirmed, next, two packets are continuously transmitted. In this way, as each packet is acknowledged,
The number of packets transmitted successively and sequentially is increased.

In the feedback control, in order to eliminate the error of the follow-up control, the above-described example a-3. . As shown in the ER system using rm cells (ATM-ABR), it is necessary to directly observe a target value and accurately feed back a difference from a control amount. However, in a real control system, there is a distance L between a control point and an observation point, and at least Δt = distance L
遅 延 There is a delay of the speed of light c. That is, the control amount observed at the observation point at time t is the control amount r (t−Δt) operated at the control point at time t−Δt, and the feedback information used to determine the control amount. △
This is the observation value t ago.

Therefore, in an actual feedback control system, no matter how accurate feedback is performed, Δt = 0 cannot be achieved, so that accurate follow-up control is performed, that is, | R (t) −r (t−Δt) | = 0 is impossible.

B. Avoidance-type congestion control method The avoidance-type congestion control method is a method in which each transmitting station and a receiving station negotiate for a transmission band before data transmission, and each transmitting station follows a command from the receiving station to transmit data. Is a congestion control method for controlling

According to this technique, prior to data transfer, a data transmission device transmits characteristic information of data transfer to a data transfer control device, and determines a detailed mode of data transfer from the characteristic information of data transfer and information of a data transfer medium. Then, data transfer is performed based on the mode.

Data transfer execution applications to which the avoidance type congestion control method is applied are file transfer and print service applications. The data to be transmitted by these applications exists in its entirety at the transmitting end before the start of the data transfer, and the data transfer has the following features.

Generally, the amount of transmission data is known. Also,
Even if the data volume is not known, the data volume is finite and the end of transmission is clearly present. In many such applications, control information such as the amount of transmission data is exchanged between the transmitting and receiving terminals before the start of data transfer.

An example of specific application control information serving as a basis of data transfer control information used in avoidance type congestion control is shown below.

The standard file transfer protocol f
tp (file transfer protocol)
In, at the start of data transfer, the data transmitting end notifies the data receiving end of the data amount of the file to be transferred.

The control file used by the print spooler of the UNIX operating system includes information such as the number of data files transmitted between printer spools for printing and the data amount of each file.

Further, ISO 10175: DPA (D
document Printing Application
On), the content of the print request information transmitted from the client to the print server at the time of print output includes the data amount of the document to be printed, the number of pages, the amount of each page data and the configuration content, the number of output copies, It is possible to show details of the print job such as the output time limit.

Therefore, based on the control information of the application, it is possible to derive the band use status by the data transfer.

Further, the data transfer application using the avoidance type congestion control method can determine the transmission path at the time when the control information is exchanged between the transmitting and receiving ends before the start of the data transfer. In such an application, transmission data already exists, and there is no change in the band used due to its generation, and the change can be kept constant.

When the avoidance-type congestion control method is used, it is a necessary condition to completely control the state of each data transfer in order to completely prevent congestion. In conventional networks in general before avoidance-type congestion control was proposed,
The application that performs the data transfer is indefinite, and it is impossible to control the status of the data transfer in a centralized manner. Therefore, the transmitting end of each data transfer has been controlled independently and plurally.

However, in a client-server type application such as a print service, all data transfer is concentrated on the server. Therefore, in the server, the start time, end time, transmitting end,
It is possible to easily obtain control information such as fluctuations in the receiving end, the route, the amount of transmission data, and the used band, and the avoidance-type congestion control method has been realized by using these control information.

In order to ascertain the actual band use situation of the transmission medium constituting the network, it is necessary to observe the band use situation at each transmission medium. However, it is generally impossible to simultaneously observe and aggregate the usage statuses of all transmission media constituting a network. However, by observing the configuration of transmission media in the network and their respective transmission capabilities, and observing the bandwidth usage status of each data transfer in the server, it is possible to infer the bandwidth usage status of each transmission medium in the network. Thus, congestion is prevented by avoidance type congestion control.

In the case of using the avoidance type congestion control system, the condition is that the data to be transmitted is allowed to be adjusted in the use band and is controllable data. In conventional networks before using the avoidance type congestion control method, the application that performs data transfer is undefined, all data transfer requests by applications are handled in the same way, and transfer is performed only from the viewpoint of high-speed processing. Congestion occurred frequently.

However, among applications that perform data transfer, applications such as file transfer and print service have a relatively large allowable range of data transfer delay, so that the start time and end time of data transfer can be adjusted. is there. In addition, since the amount of data transmitted by these applications is relatively large and the unit of the fluctuation of the band use state is long, the control is relatively easy.

Focusing on data characteristics and a concentrated form of data transfer in a client-server type application such as a print service, the requirements for realizing centralized transmission control based on a deterministic band use situation are prepared. . Therefore, in a network in which data transfer is mainly performed by an application that satisfies the requirement, it is possible to avoid contention by applying unified transmission control based on a deterministic band use situation. The avoidance type congestion control is executed based on such a condition.

Next, an example of information included in general data transfer control information in a data transfer application used for avoidance type congestion control will be described. 1. Data transmission device identifier Generally indicates the name of a data transmission station. 2. Data Transfer Identifier In general, a single data transmitting station may perform a plurality of data transfers at the same time, and at this time, identifies which data transfer is the data transfer information. 3. Proof of validity of data transfer information Prove that it is valid data transfer information. 4. Data transfer path Generally, simply indicates the name of the data receiving station. To be exact,
Indicates the identifier of the data transfer path or the identifier of the transmission medium used on the path. 5. Transmission data amount Indicates the amount of data transmitted during one data transfer period. When indicating the end of the data transfer, for example, the transmission data amount = 0
And 6. Data transfer start period Indicates the start time and end time of the period during which data transfer can be started. 7. Data transfer end period Indicates the start time and end time of the period in which data transfer should be completed. 8. Requested range of used transmission band Indicates the range of used band required for data transfer. 9. Control range of used transmission band Indicates the range of the used band that can be operated in the data transmission station. 10. Priority of data transfer bandwidth allocation Used when it is possible to specify the order and priority between data transfers.

In the above, Except for the data transmission device identifier, there is a case where it is not explicitly specified in the data transfer information depending on the implementation configuration.

When a data transfer instruction is determined based on the data transfer control information created by the application and the result is notified to the application, if any of the above conditions in the data transfer control information is not satisfied,
The application is notified of a data transfer instruction indicating that the transmission request of the content indicated in the transmission control information cannot be accepted. In this case, no data transfer instruction is issued to the transmitting device.

In the case other than the case where the application creates the data transfer control information and notifies the application of the determination result of the data transfer instruction based on the data transfer control information, If any of these conditions are not met, those conditions are ignored.

Next, an example of the information specified in the transmission instruction in the data transfer using the avoidance type congestion control is shown below. 1. Data transfer start period Specify the start time and end time of the period in which data transfer should be started. If you simply want to start sending immediately,
For example, start time = current, end time = current or indefinite. If the transmission request having the content indicated in the transmission control information cannot be accepted, for example, the start time is set to be undefined or at infinity. 2. Data transfer identifier Identifies which data transfer is the transmission instruction. 3. Data transfer end (stop) period Indicate the start time and end time of the period in which data transfer should be ended (stopped). When simply instructing the transmission end (stop) time limit, for example, the start time = current or indefinite, and the end time = transmission end (stop) time limit. Also, when simply instructing an immediate transmission stop, for example, the start time = current or indefinite, and the end time = current. 4. Data transfer path Indicates the path to be used for data transfer or the transmission medium. Alternatively, simply specify the receiving terminal. 5. Transmission data amount One transmission instruction indicates the range of the data amount permitted to be transmitted. 6. Used transmission band Specify the range of the used band.

By performing band control using these pieces of information, it is possible to achieve a high band utilization rate irrespective of the load on the transmission band and to achieve data transfer capable of obtaining accurate data transfer time prediction accuracy. Become. According to the data transfer method based on the avoidance type congestion control method, congestion between data transfers based on a specific application, for example, between block transmission traffics is avoided.

In such an avoidance type congestion control system, the receiving station distributes the bandwidth of the transmission channel to each transmitting station,
Although congestion does not occur in principle, on the other hand, each transmitting station has a delay from the generation of a transmission request to the start of transmission.

The avoidance type congestion control method can be applied to data transfer satisfying the following conditions. 1. All transmitting stations must follow the instructions from the receiving station. 2. The transmission request must allow a delay until the start of transmission.

Next, the types of packet traffic in the data transfer network will be described. Packet traffic on a transmission channel results from data transmission between a transmitting station and an application running on a receiving station. There are three types of packet traffic: a) sporadic traffic, b) narrow-band burst traffic, and c) wide-band burst traffic, each of which has different characteristics depending on the source application. Have.

A) Sporadic traffic This is traffic by an application such as RPC (remote procedure call) in a distributed processing environment.

The contents of the transmission data are a processing request message exchanged between the remote CPUs and a processing result message corresponding to the processing request message. For the efficiency of the distributed processing, it is required that the delay from the generation of the message transmission request to the start of the transmission is small. Request.

In addition, it is assumed that transmission errors rarely occur because delays due to retransmission also pose a problem. However, in general, the amount of transmission data per transmission is small and traffic generation is sporadic. Therefore, it is unlikely to cause congestion, and is not easily affected by packet loss due to congestion.

B) Narrow-band burst traffic This is traffic caused by a file transfer application or a time-series data transmission application such as audio / video, and a large amount of data spanning a plurality of packets is transmitted.

The two are positioned as narrow bands for the following reasons. With the improvement of VLSI technology and optical fiber technology, the bandwidth of the transmission channel has been widened to the order of several hundred mega to several giga bits / second.

In the file transfer, the file stored in the transmitting station is divided into packets, transmitted sequentially, and reconstructed in the receiving station. Conventionally, a large-capacity storage medium such as a magnetic disk is used for storing files, and the data input / output bandwidth is several to several tens of megabits / second (1 mega is 10 to the sixth power). The band is narrower than the band of the channel, and the band used by the traffic is also limited by the band.

In time-series data transmission, the band used is tens to hundreds of kilobits / second (one kilo is 10
3)), and even for moving images,
This is about bits / second (1 mega is 10 to the power of 6), which is about the same as the bandwidth used for file transfer.

In such an application, since packets are transmitted continuously, it is likely to cause congestion. However, even if congestion occurs, in file transfer, packet loss is partial because individual traffic is narrow band, and the time required for file transmission is sufficiently long compared to the round trip time, Retransmission is not a problem. In the case of time-series data transmission, the demand for immediacy is high,
Naturally, retransmission is inappropriate, and error correction using a redundant code is performed, so that packet loss does not pose a problem.

C) Broadband Burst Traffic In recent years, a print service application for printing and outputting a high-definition full-color image at a high speed is approaching practical use. In this case, a high-definition full-color image of several hundred megabits per page is used. , Hundreds of mega-
Continuous transmission over a wide band of bits / second is required.

As a method for responding to such a transmission request, a block transmission method has been proposed. In the block transmission method, the transmitting station, which has conventionally been a bottleneck, and
Conventionally, by using a large amount of a wideband storage medium such as a semiconductor memory to store the receiving station, the throughput of data input / output is secured, and transmission processing is performed in units of large-sized blocks in which a plurality of packets are aggregated. The overhead of transmission processing caused by the sequential transmission of units is reduced, and a wide band is obtained.

However, on the other hand, since it can be used to the same extent as the bandwidth of the transmission channel, congestion easily occurs when multiplexing with other traffic. Also, when congestion occurs, because of the wide bandwidth, it is susceptible to packet loss,
Transmission efficiency is significantly reduced, and it is difficult to achieve the bandwidth required by the application.

In a conventional distributed processing environment, a recovery-type congestion control method is inevitably adopted due to the characteristics of sporadic traffic, and other existing traffic is also narrow-band traffic. Was satisfied.

On the other hand, in the case of wideband burst traffic, it is important to avoid congestion due to its characteristics, and in principle, recovery type congestion control which cannot avoid this is not applicable.

The above will be described with reference to the following equation and FIG. Conventional traffic is an area where the bandwidth used per one traffic shown by hatching in the lower left portion in FIG. 2 is narrow, and the influence of transmission errors due to congestion was small. However, the wideband burst traffic indicated by the hatched area in the upper right of FIG. 2 uses a wide bandwidth up to the same level as the bandwidth of the transmission channel per traffic, and therefore, transmission errors generated during congestion increase. Also, as shown in the following equation,
In block transmission, since block errors occur exponentially according to the number of packets constituting a block, it is not possible to apply recovery-type congestion control that cannot in principle avoid congestion.

[0080]

P _blk = 1− (1−P _pkt ) ^Npkt P _blk : Probability of occurrence of transmission error in one block P _pkt : Probability of packet loss N _pkt : Number of packets in one block

In the case where only the broadband burst traffic is multiplexed, the conditions are narrowed down and a configuration to which the avoidance type congestion control method is applied is disclosed in Japanese Patent Application No. 08-17949 (February 2, 1996).
Application).

The configuration disclosed in Japanese Patent Application No. 08-17949 provides a data transmission technique capable of obtaining high bandwidth utilization efficiency and accurate data transmission time prediction accuracy regardless of the load on the transmission band. It is a configuration aiming at The start time, end time, transmitting terminal, receiving terminal, route, of each data transmission of broadband burst traffic,
To grasp the transmission status such as the change of the band used and to make such information deterministically known. 2. Each data transmission is controlled in a unified manner, and the band usage status of all data transmissions is controlled, and the fixed value control is performed with the control amount being the bandwidth usage amount of all transmissions and the target value being the maximum transmission bandwidth of the transmission medium. ing.

The configuration disclosed in Japanese Patent Application No. 08-17949 has a configuration for accurately acquiring the bandwidth utilization status of each broadband burst traffic data transmission. Japanese Patent Application 08-
In 17949, data to be transmitted by an application that performs data transmission is only data that exists entirely at the transmitting end before the start of data transmission. In an application to which the avoidance type congestion control method is applied, control information such as a transmission data amount is exchanged between the transmitting and receiving terminals before the start of data transmission.

With this avoidance type congestion control system, congestion due to multiplexing of wideband burst traffic is solved. However, the avoidance type congestion control method disclosed in Japanese Patent Application No. 08-17949 cannot solve the occurrence of congestion due to multiplexing of one broadband burst traffic and conventional traffic. In a data transfer network, various types of data are transferred.
Or, if data transfer is performed by the avoidance control method, it is difficult at present to control the bandwidth of the entire network.

Most of the conventional traffic performs recovery-type congestion control for the above-mentioned reason, and its transmitting station performs band setting independently of the transmitting station, and performs avoidance-type congestion control from the receiving station. Do not follow instructions.

Therefore, a technique for estimating the bandwidth used by other traffic when starting transmission of wideband burst traffic and avoiding congestion by using the remaining transmission channel bandwidth is described in "Data Transfer Apparatus and Method" (Heisei 9).
Filed on June 3, 2012 by the inventor Koichi Yoshimura).

However, this method is based on the premise that the bandwidth used by other traffic does not fluctuate during transmission of wideband burst traffic, and as shown in FIG. 3, the bandwidth used by other traffic increases on the way. If the total bandwidth used with the wideband burst traffic exceeds the bandwidth of the transmission channel, there is a problem that congestion occurs.

FIG. 3 shows a relationship between data transmission from a plurality of transmitting stations to a receiving station and each band.
When a plurality of transmitting stations on the left side of FIG. 3 execute data transmission in each band at an arbitrary timing, a region indicated by a hatched portion of a used band graph on the receiving station side exceeds a transmission channel band, and as a result, This indicates that congestion occurs.

[0089]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and dynamically controls the transmission bandwidth of wideband burst traffic in accordance with the increase in the bandwidth used by other traffic. It is another object of the present invention to provide a data transmission technique capable of executing high bandwidth utilization efficiency and accurate data transmission regardless of the load on the transmission band.

[0090]

The following hints can be obtained by focusing on the fact that congestion is mainly caused by conventional narrow-band burst traffic when multiplexing with wide-band burst traffic.

1) Conventional narrow-band burst traffic The bandwidth used by each traffic is relatively stable as described above. In other words, from the viewpoint of broadband burst traffic,
The increase in bandwidth used for other traffic is due to the occurrence of new narrow-band burst traffic.

2) Normally, when transmitting a continuous series of packets, such as narrow-band burst traffic, connection-oriented transmission is performed. In other words, instead of securing resources such as transmission / reception buffers individually for each packet,
By previously securing resources to be repeatedly used for a series of packets, overhead for each packet is reduced.

For this reason, a message for connection is exchanged between the receiving station and each transmitting station prior to traffic generation.

3) Applications that generate narrow-band burst traffic are fixed and can be limited for each packet switching network, such as ftp, lpr, or rprint.

The data transmission apparatus and data transmission method of the present invention provide a new narrow band burst
Prior to the occurrence of traffic, by utilizing the fact that connection messages are exchanged between transmitting and receiving stations, as a result, within the time until the total bandwidth usage increases, the transmission bandwidth of wideband burst traffic is suppressed, Avoid congestion due to control delay.

To achieve the above object, a data transmission apparatus according to the present invention comprises a data transmission station, a data reception station, and a data transmission channel for transmitting data packets from the data transmission station to the data reception station. In the data transmission apparatus, the data transmission station controls a transmission band of a data transmission channel used for data transmission from the data transmission station to the data reception station based on a transmission band instructed by the data reception station. Means for transmitting data to a data receiving station based on the transmission band controlled by the transmission band control means, wherein the data receiving station comprises a transmission channel for receiving data packet traffic. A use band measuring means for measuring a use band; and data transmission other than the data transmission station transmitting data to the data reception station. A connection detecting means for detecting a connection message relating to a new data packet transmission using a transmission channel from the station to the data receiving station, a current bandwidth of the transmission channel measured by the bandwidth measuring means, and a connection detecting means. A new transmission band of the data transmitting station transmitting the data packet is determined so that the sum of the estimated use band and the estimated use band generated by the transmission of the new data packet based on the detected connection message does not exceed the band of the transmission channel. Transmission band determining means for notifying the data transmission station of the determined new transmission band.

Further, the data receiving station in the data transmission apparatus of the present invention has a table of a protocol identifier and a connection identifier corresponding to an application, and the connection detecting means detects the protocol identifier and the connection identifier included in the received packet. Identify applications based on
A connection message is detected.

[0098] The connection detecting means in the data receiving station in the data transmission apparatus of the present invention is provided for each application that executes data transmission and reception, and detects connection messages by exchanging connection messages in each application. And

Further, the data receiving station in the data transmission apparatus of the present invention has a correspondence table of the estimated use bandwidth for each application, and determines the estimated use bandwidth of the application in which the connection message is detected based on the correspondence table. It is characterized by having a configuration.

Further, the data transmission method according to the present invention provides a data transmission method in a data transmission apparatus including a data transmission station, a data reception station, and a data transmission channel for transmitting a data packet from the data transmission station to the data reception station. In the method, the data receiving station measures a used band of a transmission channel of the received data packet traffic, and a data transmitting station other than the data transmitting station transmitting data to the data receiving station. A connection detecting step of detecting a connection message relating to a new data packet transmission using a transmission channel to the data receiving station, a current band of the transmission channel measured by the band measuring unit, and a connection detected by the connection detecting unit. New data packet transmission based on the connection message A new transmission band of the data transmitting station transmitting the data packet is determined so that the sum of the estimated estimated usage band and the resulting transmission band does not exceed the band of the transmission channel, and the determined new transmission band is transmitted to the data transmitting station. A transmission band determination step of notifying the data transmission station of the data reception station based on the new transmission band determined by the transmission band determination step of the data reception station. A transmission band control step of controlling a transmission band of a data transmission channel to be used, and a data transmission step of transmitting data to a data receiving station based on the transmission band controlled by the transmission band control step. Features.

In the data transmission method according to the present invention, the change of the data transmission band in the data transmission station in the transmission band control step is performed when a new data transmission from the other transmission station is performed based on the connection message detected by the data reception station. It is characterized in that it is performed at a time before an increase in the use band of a transmission channel due to packet transmission occurs.

Further, the data receiving station in the data transmission method of the present invention has a table of a protocol identifier and a connection identifier corresponding to a specific application, and the connection detecting step in the data receiving station includes the step of detecting the protocol included in the received packet. Identifying an application based on the identifier and the connection identifier.

The connection detecting step in the data receiving station in the data transmission method of the present invention is executed by a step of exchanging connection messages for each application that executes data transmission and reception.

Further, the data receiving station in the data transmission method of the present invention has a correspondence table of the estimated use bandwidth for each application, and determines the estimated use bandwidth of the application in which the connection message is detected based on the correspondence table. With steps.

[0105]

FIG. 4 shows the configuration of one embodiment of the data transmission apparatus of the present invention.

The main components of the data transmission apparatus of the present invention are a data transmission station, a data reception station, and a data transmission channel for performing data transmission between the data transmission station and the data reception station.

The transmitting station in the data transmitting apparatus of the present invention is different from the receiving station in the data transmitting apparatus of the present invention in that:
It has a transmission band control means 1 for performing block transmission by wideband burst traffic.

The transmission band control means 1 executes control such as starting data transmission and changing the band of data transmission according to the transmission instruction notified from the receiving station.

The receiving station in the data transmitting apparatus of the present invention multiplexes broadband burst traffic from the transmitting station of the data transmitting apparatus of the present invention with conventional traffic from other transmitting stations on the same transmission channel. It receives packet traffic, and has a used band measuring unit 2, a connection detecting unit 3, and a transmission band determining unit 4.

The used band measuring means 2 measures the total used band by the packet traffic multiplexed on the transmission channel and received by the receiving station.

The connection detecting means 3 detects a connection message exchange performed prior to the start of transmission of the conventional narrow-band burst traffic.

The transmission band determining means 4 outputs a wide band burst
At the start of traffic transmission, an initial value of the transmission band of the wideband burst traffic is determined based on the measurement result of the bandwidth used by the packet traffic multiplexed on the transmission channel, and transmitted to the transmitting station of the data transmission apparatus of the present invention. And instruct.

Further, when the exchange of the connection message is detected during the period of the broadband burst traffic, the transmission band determining means 4 determines the change value of the transmission band of the wideband burst traffic and determines the change value. The change value is instructed to the transmitting station of the data transmission device of the present invention.

An embodiment of the transmission band control means 1 in the transmitting station will be described with reference to FIG. The transmission band control means 1 has a packet transmission function 11 and a transmission interval counting function 12.

The packet transmission function 11 divides the transmission data S01 of the application into packets,
2, the packet is transmitted to the transmission channel for each packet. Packet transmission is performed for each start signal S11 from the transmission interval counting function 12.

The transmission interval counting function 12 has a transmission interval TTx
The packet transmission instruction signal S11 is notified to the packet transmission function 11 every time is counted. The clock for counting is arbitrary, and includes a transmission clock to the transmission channel or a reception clock pulled from the transmission channel. The transmission interval TTx is given by the following equation with respect to the packet length L and the designated transmission band RTx notified by the signal S03.

[0117]

TTx = L / RTx

The initial value of the transmission interval TTx is infinite, that is, the transmission is stopped. The transmission counting function obtains the corresponding transmission interval T by the above equation every time the instruction of the instruction transmission band RTx larger than zero is received by the signal S03, and thereafter, every time the interval T is counted, the transmission start is notified by the signal S11. I do. The above operation will be described with reference to FIG.

In FIG. 6, when the operation of the transmission band control means starts (step 601), first, the transmission interval T
The initial value of Tx is set to infinity (∞) (Step 602)
Is done. Next, in steps 603 and 611, an instruction for the transmission band RTx by a signal from the receiving station is waited. When TTx = ∞ and there is no instruction of the transmission band RTx from the receiving station to the transmitting station, a loop is performed between step 603 and step 611. When the receiving station instructs the transmitting station about the transmission band RTx, in step 604, the transmission interval TTx is determined based on the packet length L and the indicated transmission band RTx, TTx = L / RT.
x. In step 605, the time T to be measured is set to T = TTx, and in step 606,
The time is measured by T = T-ΔClock. When the elapse of the time T is confirmed in step 607, the process proceeds to step 608, and the packet is transmitted. Step 607
If the time T has not elapsed, the process returns to step 603.
When the packet transmission in step 608 is completed, T = TTx is set again in step 609, and the process returns to step 603 until the transmission is determined to be completed in step 610, and the same steps are repeated for the next packet transfer.

Next, an embodiment of the used band measuring means 2 will be described with reference to FIG. The used band measuring means 2 has a packet receiving function 21 and a receiving interval counting function 22.

Each time a packet S02 multiplexed on a transmission channel to a receiving station is received, the packet receiving function 21 notifies the reception of the packet by a signal S21. The received packet S04 is output to the application

Receiving the notification of the packet reception by the signal S21, the reception interval counting function 22 starts counting the reception interval TRx, and thereafter, every time a new packet is notified, the band used by the signal S05 is used. Output RRx. The used band RRx is given by the following formula with respect to the packet L and the reception interval TRx.

[0123]

RRx = L / TRx

Next, an embodiment of the connection detecting means 3 will be described with reference to FIG. The connection detecting means 3 has a packet inspection function 31. The packet inspection function 31 detects a connection message in a packet sent via the transmission channel.

The connection message of the specific application can be detected by checking the protocol identifier and the connection identifier of the received packet. Since data of each application is packetized and transmitted using the function of a layered protocol, it generally has a structure shown in FIG. That is, the information of the protocol of the layer (N) includes information designating the next higher layer (N + 1) protocol, and this is the protocol identifier. When a plurality of applications simultaneously perform data transmission using the same protocol, the packet includes information for identifying the destination application, which is a connection identifier. Examples of the connection identifier include a port number in UDP and TCP, and a VPI / VCI (virtual path identifier / virtual channel identifier) in ATM.

The packet inspection function holds a table of protocol identifiers and connection identifiers corresponding to a specific application to be detected as shown in FIG. 10, and inspects the protocol identifiers and connection identifiers of the received packet S05. When both identifiers match the entry in the table, the application which has detected the connection message is notified by signal S06.

Further, as an embodiment of the connection detecting means, the connection detecting means is provided for each application for transmitting the narrow-band burst traffic on the receiving station. May be notified to the signal S06.

Next, an embodiment of the transmission band determining means 4 will be described with reference to FIG.
This will be described below. The transmission band determination means 4 has an increase band estimation function 41 and a transmission band instruction function 42.

The increase band estimation function 41 holds the use band per traffic corresponding to each application in a table as shown in FIG.
When the connection message is detected, a use band corresponding to the connection message is obtained, and is notified as a presumed increase band by a signal S41.

The transmission band instructing function 42 stores the used band notified by the signal S05, and when starting transmission of wideband burst traffic, subtracts the used band from the band of the transmission channel to indicate the remaining transmission band: RTx As a signal S03, and this is stored. Further, when the estimated increase band is notified by the signal S41 during the transmission of the wideband burst traffic, the change value of the instruction transmission band of the wideband burst traffic: RTx ′ is calculated again,
Instructed by the signal S03, and this is stored. The changed value of the designated transmission band: RTx ′ is the current designated transmission band: RT
x, transmission channel band: Rchannel, current band used: Rcurrent, and estimated increase band: R
Delta is given by the following equation.

[0131]

## EQU4 ## RTx ′ = RTx− (Rcurrent + Rd)
eta-Rchannel)

The current instruction transmission band: RTx is changed to the change value of the transmission band obtained by the above equation: RTx ′, and packet transmission is executed, thereby causing contention and congestion exceeding the transmission channel band: Rchannel. Can be prevented.

As described above, the data transmission apparatus and method of the present invention dynamically control the transmission band of data transmission, and the effect is remarkable when the utilization rate of the transmission channel is high. FIG. 13 shows the effect of the present invention. In the conventional congestion control method, as the utilization rate of the transmission channel increases, the transmission efficiency sharply decreases. However, according to the configuration of the present invention, even in a situation where the utilization rate of the transmission channel is high, the band setting and the change are performed in consideration of the used band, so that the transmission efficiency does not decrease.

[0134]

As described above, according to the data transmission apparatus and the data transmission method of the present invention, the wideband burst traffic is multiplexed with the conventional traffic transmitted from the plurality of transmitting stations at arbitrary timings. Even when the transmission is performed, the transmission band of the wideband burst traffic is dynamically suppressed prior to the increase of the band used by other traffic, so that even at a band usage rate close to 100% of the transmission channel band, High transmission efficiency can be obtained by avoiding congestion due to control delay and preventing packet loss.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of congestion in a multiplexing buffer.

FIG. 2 is an explanatory diagram of a relationship between a traffic use band and packet loss at the time of congestion.

FIG. 3 is an explanatory diagram of congestion due to an increase in the bandwidth used by other traffic during wideband burst traffic transmission.

FIG. 4 is an explanatory diagram of a means configuration of a data transmission device of the present invention.

FIG. 5 is an explanatory diagram of an embodiment of a transmission band control means.

FIG. 6 is an explanatory diagram of an operation example of a transmission band control unit.

FIG. 7 is an explanatory diagram of an embodiment of a used band measuring unit.

FIG. 8 is an explanatory diagram of an embodiment of a connection detecting means.

FIG. 9 is an explanatory diagram of a packet structure.

FIG. 10 is an explanatory diagram of a monitoring packet table.

FIG. 11 is an explanatory diagram of an embodiment of a transmission band determining unit.

FIG. 12 is an explanatory diagram of an application estimation use band table.

FIG. 13 is an explanatory diagram of effect prediction of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 transmission bandwidth control means 2 usage bandwidth measurement means 3 connection detection means 4 transmission bandwidth determination means 11 packet transmission function 12 transmission interval counting function 21 packet reception function 22 reception interval counting function 31 packet inspection function 41 increase bandwidth estimation function 42 transmission bandwidth instruction Function S01 Input data from application S02 Packet S03 Notification of instruction transmission bandwidth S04 Output data to application S05 Notification of bandwidth used S06 Connection message detection notification S11 Packet transmission instruction S21 Packet reception notification S41 Estimated increase bandwidth

Claims (9)

[Claims] 1. A data transmission apparatus including a data transmission station, a data reception station, and a data transmission channel for transmitting a data packet from the data transmission station to the data reception station, wherein the data transmission station comprises: A transmission band control means for controlling a transmission band of the data transmission channel used for data transmission from the data transmission station to the data reception station based on a transmission band instructed by the data reception station; Data transmission means for transmitting data to the data receiving station based on the controlled transmission bandwidth, wherein the data receiving station measures a bandwidth used by the transmission channel for received data packet traffic. A band measuring means, and a data transmitting station other than the data transmitting station transmitting data to the data receiving station. Connection detection means for detecting a connection message relating to new data packet transmission using the transmission channel to the data receiving station; current usage bandwidth of the transmission channel measured by the usage bandwidth measurement means; Means for transmitting a new data packet based on the connection message detected by the means, and a new transmission of the data transmitting station transmitting the data packet so that the sum of the estimated used bandwidth and the estimated used bandwidth does not exceed the bandwidth of the transmission channel. Determine the bandwidth,
A transmission band determining unit for notifying the data transmitting station of the determined new transmission band. 2. The data receiving station has a table of a protocol identifier and a connection identifier corresponding to an application, and the connection detecting means specifies the application based on the protocol identifier and the connection identifier included in a received packet. The data transmission device according to claim 1, wherein the connection message is detected. 3. The connection detecting means in the data receiving station is provided for each application that executes data transmission and reception, and detects the connection message by exchanging connection messages in each application. 2. The data transmission device according to 1. 4. The data receiving station has a configuration in which a correspondence table of an estimated usage bandwidth for each application is provided, and the estimated usage bandwidth of the application in which the connection message is detected is determined based on the correspondence table. The data transmission device according to claim 2 or 3, wherein 5. A data transmission method in a data transmission device, comprising: a data transmission station; a data reception station; and a data transmission channel for transmitting a data packet from the data transmission station to the data reception station. A station for measuring a band used by the transmission channel for received data packet traffic; and a step for measuring data from another data transmitting station other than the data transmitting station transmitting data to the data receiving station. A connection detection step of detecting a connection message relating to a new data packet transmission using the transmission channel to a receiving station; a current use band of the transmission channel measured by the use band measurement unit; and the connection detection unit New data packet based on detected connection message So that the sum of the estimated bandwidth in use caused by feed does not exceed the bandwidth of the transmission channel, to determine the new transmission band of the data transmitting station transmitting data packets,
A transmission band determining step of notifying the determined new transmission band to the data transmission station, wherein the data transmission station determines the new transmission band determined by the transmission band determination step of the data reception station. A transmission band control step of controlling a transmission band of the data transmission channel used for data transmission from a data transmission station to a data reception station, based on the transmission band controlled by the transmission band control step, A data transmission step of transmitting data to a receiving station. 6. The change of the data transmission band by the transmission band control step in the data transmitting station is performed by transmitting the new data packet from the other transmitting station based on a connection message detected by the data receiving station. 6. The data transmission method according to claim 5, wherein the method is performed at a time before an increase in the band used by the channel occurs. 7. The data receiving station has a table of a protocol identifier and a connection identifier corresponding to a specific application, and the step of detecting the connection in the data receiving station includes the step of detecting a protocol identifier and a connection identifier included in a received packet. 7. The data transmission method according to claim 5, further comprising the step of specifying an application based on the data. 8. The data transmission method according to claim 5, wherein the connection detecting step in the data receiving station is performed by a step of exchanging connection messages for each application that executes data transmission / reception. 9. The data receiving station has a correspondence table of an estimated use bandwidth for each application, and has a step of determining an estimated use bandwidth of the application in which the connection message is detected based on the correspondence table. 9. The data transmission method according to claim 7, wherein: