JPH1028123A - Network data communication method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To perform data communication with optimal transmission quality according to the use state of a network during data transfer. SOLUTION: A plurality of ATMs are connected between ATM terminals 10 ₁ and 10 _2.
In a data communication system of a network for communicating data through an ATM network 11 having a TM switch,
If the communication parameters are unknown in advance, the ATM on the transmitting side
The terminal includes a first connection generating means 12 for generating a connection between the ATM exchanges using UBR, and after generating the connection, divides the data into cells and transmits the data.
Transmission statistics collecting means 134 for collecting transmission statistics on a cell basis
And determine communication parameters based on the transmission statistics,
Second connection generation means 12 for generating a new connection between ATM exchanges using CBR,
This is a network data communication system for performing data communication by switching to this new connection.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data communication system of a network for performing data communication between a plurality of devices including a computer and other devices.

[0002]

2. Description of the Related Art Conventionally, networks for performing data communication between a plurality of devices include an ATM (Asynchronous Transfer Mode) system network and an Ethernet network.

In this ATM network, as shown in FIG. 17, ATM switches SW1 to SW4, which are a number of ATM switches, are interposed between a terminal A1 and a terminal A2.
Prior to data transmission, a virtual connection is set up, the data to be transmitted over this set communication path is divided into cells of a predetermined length, and a header containing connection information such as the destination is added to each cell. This is a method of transmitting data to the partner terminal.

Therefore, for example, when data is transmitted from the terminal A1 to the terminal A2, it is necessary to set up a virtual connection between the terminal A1 on the transmitting side and the terminal A2 on the receiving side. When setting this virtual connection, the ATM switch S
Signaling is performed with W1. That is, the terminal A1 on the transmitting side notifies the ATM switch SW1 of the address of the terminal A2 on the receiving side and identifiers for connection such as a virtual path identifier VPI and a virtual channel identifier VCI. At this time, transmission quality parameters required for data transmission such as a data transmission band and a data transmission type are also notified.

[0005] Here, the ATM switch SW1 determines a route that satisfies the required transmission quality while exchanging information with another ATM switch based on the header information, and sets a virtual connection. When the virtual connection is set in this manner, the transmitting terminal A1 transmits data through the connection within a range in which the transmission quality requested at the time of signaling is maintained.

Next, the Ethernet network is C
In the SMA / CD bus LAN, a plurality of hubs 102 ₁ , 102 ₂ ,... Called hubs are branched on a common transmission cable 101 as shown in FIG.
A plurality of terminals B1,..., A plurality of terminals B2,... Are connected to these concentrators 102 ₁ , 102 ₂ , respectively, and data is transferred in only one direction between the terminals B1 and B2. 103 is a terminator (terminator).

[0007] When sending data from the terminal B1 to the terminal B2, terminal B1, the other terminal via the concentrator 102 ₁ checks whether or not using the network. If the network is not used, the corresponding concentrator 1
The data is transferred onto the transmission cable 101 via the transmission cable 02 ₁ . This transfer data is basically sent to all terminals connected in the network. Therefore, after receiving the data, each terminal checks the destination, and if it is addressed to itself, takes in the data as it is, and if not addressed to itself, discards the received data. If two or more terminals accidentally transfer data at the same time, the data will not be transferred correctly due to data collision.Therefore, multiple terminals that have sent data wait for a random time with each other, check the network usage status, and check that the network is free. If so, transfer the data again.

[0008]

Therefore, in the above-described ATM network, the transmission quality of the virtual connection can be requested only at the time of connection setting by the first signaling, and cannot be requested at the stage of data transfer.
As a result, there is a problem that transmission quality parameters cannot be changed even if the usage state of the entire network changes during data transfer.

On the other hand, in the Ethernet network, when transferring a large amount of data such as a file transfer, there is a problem that one terminal occupies the network for a long time and another terminal cannot use the network. For example, when using a control device of a plant, if the network is in a state of being unable to communicate for a long time, and even if an abnormality occurs in a plant controlled by the control device, the condition is notified to a higher-level device. Difficult
There is a problem that can lead to the suspension of operation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a network data communication system which can change the transmission quality of data transfer according to the network conditions during data transfer.

Still another object of the present invention is to provide a network data communication system which enables another terminal to use the network even when a certain terminal continuously transfers a large amount of data.

[0012]

According to a first aspect of the present invention, there is provided a data communication system for transmitting data through an ATM network having a plurality of ATM exchanges between ATM terminals, wherein a communication parameter is unknown in advance. The ATM terminal on the transmitting side communicates with an ATM exchange constituting the ATM network through UBR (Unspecifiable).
i-ed Bit Rate) first connection generating means for generating a first connection using a service category;
After the first connection is generated, data is actually divided into cells and transmitted, and transmission statistics collecting means for totalizing transmission statistics on a cell-by-cell basis; a communication parameter is determined based on the totaled transmission statistics; CBR (Constant Bit Rate) or VBR (Variab)
le bit rate) to generate a new second connection.
This is a data communication method of a network that performs data communication by switching to the connection.

According to the invention corresponding to claim 1, by taking the above means, prior to data transmission, when the communication parameters are unknown in advance, a first connection is generated using UBR, The data is actually transmitted, transmission statistics are totaled, and communication parameters are determined. Then, based on the determined communication parameters, CBR or V
Since a new second connection is generated using the BR and data is communicated under the second connection, data communication can be performed according to the transmission capability even when communication parameters are unknown in advance.

According to a second aspect of the present invention, in a data communication system of a network for communicating data between ATM terminals through an ATM network having a plurality of ATM exchanges, the transmitting-side ATM terminal performs data communication after generating a connection. A transmission statistics collection unit that compiles transmission statistics on a cell basis during the communication, and compares a communication parameter obtained from the collected transmission statistic with a communication parameter of a connection currently being communicated. Connection processing control means for generating a new connection based on the communication parameter obtained from the transmission statistics when the parameter value exceeds a desired parameter value range than the communication parameter of the currently communicating connection; Of a network that performs data communication by switching to a connection This is a data communication method.

According to the second aspect of the present invention, by taking the above-described means, the state of the network is checked for each cell, and the communication parameters of the network are determined by the communication parameters of the connection currently being communicated. When it is far from the situation, a new connection is created and the data is communicated by switching to the newly created connection. Communication can be performed.

According to a third aspect of the present invention, there is provided a data communication system for providing an ATM network having a plurality of ATM exchanges between Ethernet terminals at both ends and communicating data in a frame format. Bridges are respectively provided between the network and the Ethernet terminal, and the Ethernet terminal uses TCP (Transmis
sion Control Protocol) / IP (Internet Protocol)
) Embedded in an ATM signaling message in a data frame with
This is a network data communication system for extracting an ATM signaling message from the received data frame, performing signaling to the ATM network, and performing data communication in a frame format.

According to a third aspect of the present invention, each of the bridges extracts an ATM signaling message from a frame sent from an Ethernet terminal and performs signaling to the ATM network. By performing the above, the VCC is generated and data communication is performed, so that data communication can be performed between terminals that handle data in a frame format while maintaining ATM communication quality.

According to a fourth aspect of the present invention, there is provided a data communication system for a network in which a connection-type transport layer-equivalent protocol exists and a flow control using a window is performed at a transmitting terminal.
When data communication is performed from the application task to the receiving terminal via the TCP task, the TCP
The progress of the transmission window number is determined from the time-series history of the transmission window number for each TCP connection of the task, and the IPMTU of the TCP connection is determined.
(Maximum transmission unit) This is a network data communication system provided with a network monitoring task that varies the size.

According to a fourth aspect of the present invention, when the network monitoring task determines that the progress of the transmission window number is slow, it considers congestion to occur and takes the TCP connection by taking the above means. The IP MTU size of the TCP connection, and conversely, when it is determined that the progress of the transmission window number is smooth, the IP MTU size of the TCP connection is increased, thereby reducing the packet loss rate of IP packets during congestion. Can be.

According to a fifth aspect of the present invention, there is provided a data communication system for providing an ATM network between Ethernet terminals at both ends and communicating data in a frame format, wherein each of the Ethernet terminals is provided between the Ethernet terminal and the ATM network. A bridge is provided, and the Ethernet terminal embeds an ATM signaling message and a band reservation message in a data frame having TCP / IP and transmits the data frame, and each of the bridges performs band reservation from among the received data frames. This is a network data communication method for generating a VCC according to the request reservation content of the bandwidth reservation message by performing the ATM signaling when a message is extracted.

According to a fifth aspect of the present invention, when the bridge extracts a bandwidth reservation message from a data frame by generating the above means, it generates a VCC having a bandwidth corresponding to the request. Therefore, data communication can be performed without guaranteeing the communication quality of the network without passing through a router.

According to a sixth aspect of the present invention, there is provided a data communication system for a network comprising an ATM switch and a terminal which can reserve bandwidth and other resources and performs admission control. After the traffic contract is made, the amount of data flowing through the VCC during data communication is monitored, and when the contracted amount is equal to or less than a predetermined amount and continues for a predetermined number of times per unit time, the allocated bandwidth is reduced and the transmission is performed. This is a network data communication method for notifying the terminal device.

According to the present invention, the ATM switch monitors the actual amount of data during data communication and takes much less data than the contract, by taking the above measures. Since the allocated bandwidth is reduced and the transmission side terminal is notified, the resources of the ATM exchange can be used efficiently.

According to a seventh aspect of the present invention, in a data communication system for a network in which an ATM network including a plurality of ATM switches is arranged between ATM terminals, the ATM switch has a burst tolerance with respect to a transmitting ATM terminal. The transmitting ATM terminal determines the MTU size based on the burst tolerance, determines the size of the IP packet according to the determined MTU, performs cell division, and transmits the data. It is.

According to the invention corresponding to claim 7, by taking the above-described means, the transmitting-side ATM terminal has:
Since the MTU size is determined based on the burst retransmission, it is possible to prevent the IP packet from being discarded due to the MTU size being too large.

According to an eighth aspect of the present invention, in a data communication system of a network in which a plurality of devices exchange data via a network, an Ethernet for concentrating data lines output from the plurality of devices on the network. A hub or Ethernet switch and a node for generating a delay time are provided, and when the Ethernet hub or the Ethernet switch receives data occupying a large band from a certain device, the Ethernet hub or the Ethernet switch inputs the data to the node and delays the data. This is a network data communication method that enables data communication between other devices during the delay time by returning the data to the Ethernet hub or the Ethernet switch and sending it to a desired destination.

By adopting such means, the data communication between other devices is not interrupted, and the danger that the data transfer of the emergency message is stopped for a long time can be avoided.

According to a ninth aspect of the present invention, in a data communication system of a network in which a plurality of devices exchange data via a network, an Ethernet for concentrating data lines output from the plurality of devices on the network. -Provide a hub or Ethernet switch,
The Ethernet hub or switch has a buffer for creating a delay time, and when data occupying a large band is received from a certain device, the data is input to the buffer and delayed after being received at a desired destination. This is a network data communication method that enables data communication between other devices during the delay time by transmitting the data to the other device. The invention corresponding to the ninth aspect has the same effect as the invention corresponding to the eighth aspect.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 is a block diagram showing one embodiment of a data communication system of an ATM network according to the first embodiment. For example, continuous media information such as a moving image is communicated between two ATM terminals. A valid network when you are.

In the drawing, reference numerals 10 ₁ , 10 ₂ ,... Divide data to be transmitted into cells of a predetermined fixed-length byte, transfer header data including connection information for each cell, and transfer the cells. A with the function of translating and receiving header information
TM terminals, the ATM terminals 10 ₁ , 10 ₂ ,
... a number of ATM switch 11 _1, 11 _2, ... ATM network 11 comprising more is interposed between.

Each of the ATM terminals 10 ₁ , 10 ₂ ,... Generates an end-to-end virtual connection required for user information transfer, and executes a connection end / release processing unit 12 for executing transfer end release processing. It is composed of an ATM interface card 13 which performs cell division and assembly, header translation, and grasp of a cell transfer state.

The connection creation / release processing unit 12
A program memory 121 for storing a processing program for performing connection generation (setting) control, connection release control, and other necessary processing control; a main memory or an external storage device 122 for storing moving image data and the like; It is composed of a buffer memory 123 for storing data, a connection control processing unit 124 such as a microprocessor for reading necessary processing programs from the program memory 121 and executing connection generation / release processing control.

On the other hand, the ATM interface card 13
Is an SA that has functions such as cell division and assembly and header translation.
Cell transmission for signaling the R (Segmentation And Reassembly) unit 131, the physical layer unit 132, the optical-to-electrical conversion unit 133, and the ATM network 11 to establish a VCC (virtual channel connection) and then observe the transmission rate for the VCC. It is configured by a statistics collection unit 134 and the like.

The connection creation / release processing unit 12
And the ATM interface card 13 are connected by a system bus 14. In the ATM network including the ATM terminal as described above, the ATM terminal 10 ₁
Prior to performing data communication with another ATM terminal as a communication partner, signaling performs signaling to set up a connection. However, at this stage, necessary transmission quality parameters are often unknown from the viewpoint of communication quality and transmission efficiency.

Therefore, the connection control processing unit 124 performs CBR (Co) classification as a service category of traffic to be transferred on the network according to the processing program of the program memory 121 prior to data transfer.
nstant Bit Rate), VBR (Variable Bit Rate),
UBR (Unspecified Bit Rate), ABR (Available
Bit Rate), a service category of UBR is selected as shown in FIG. 2, and a VCC (virtual connection) 1 is generated as shown in FIG. 2A without specifying detailed traffic parameters. After the connection VCC1 is generated, the moving image data is actually read from the main memory or the external storage device 122, divided into cells by the SAR unit 131, and transferred to the network. Where UBR
Is a service category in which cells are transferred if a band is available during transfer without discarding necessary bands in advance, and overflow cells are discarded if there is no space.

At this time, when the data communication using the generated VCC1 is started, the cell transmission statistics collecting section 134 observes the transmission speed of the VCC1. For example, it is the number of bytes per second, and this observation result is read by the connection control processing unit 124, and the communication parameters such as the cell speed and the burst length are determined here.

The connection control processor 124 performs CBR or VBR based on the determined communication parameters.
A new virtual connection VCC2 is generated as shown in FIG. Then, after the new connection VCC2 is generated, the data is transmitted by switching to the new connection VCC2. Here, CBR and VBR are service categories in which the ATM exchange allocates necessary bands that can guarantee required quality such as cell loss quality and cell transfer delay quality based on declaration of communication parameters from the ATM terminal. Usually, CBR or VBR is used depending on whether the generated cell interval is fixed or variable. Incidentally, when a connection is generated using CBR, for example, a peak cell rate is used as a signaling parameter as a cell rate. VB
When a connection is generated using R, the Heake cell speed is simply used as the average cell speed. However, the average cell speed and the peak cell speed in an observation range in a certain period may be measured and used as a signaling parameter.

Therefore, according to the data communication system of the above-described embodiment, even if the communication parameters are unknown in advance, the VCC1 is virtually generated using the UBR service category, and the actual VCC1 is generated. To transmit communication data to clarify communication parameters, and to provide CBR or VBR service
Since the connection of the required quality based on the communication parameter is established using the category, communication according to the transmission capability can be performed.

According to another embodiment of the present invention, for example, a plurality of receiving-side ATM terminals are installed.
Also, without installing the cell transmission statistics collection unit 134, the data transmission rate from the external storage device 122 to the ATM interface card 13 is measured by software, the cell speed and the shaving value are calculated, and a new connection is generated. May be. (Second Embodiment) An embodiment of a network data communication system according to claim 2 will be described. Since the configuration of this embodiment is the same as that of FIG. 1, the configuration will be described using the configuration of FIG.

FIG. 3 shows the intended points of this embodiment.
In the conventional case shown in FIG. 1A, after the connection is generated, all the data to be transferred is transferred, and the connection is released after the transfer is completed. As shown in FIG. 2 (b), the data communication method relating to No. 1 generates a connection VCC1 using the UBR service category, and then actually transfers data to clarify communication parameters at an appropriate time. CBR or VB based on this communication parameter
In this method, connection VCC2 is generated using R, and connection VCC3 is generated again at a desired time.

On the other hand, in the data communication system according to the second aspect, as shown in FIG. 3C, the communication parameters are clarified for each data cell, and the use status of the network is grasped for each data cell. This is a method for generating a new connection while transferring data.

Hereinafter, this embodiment will be described in detail. Now, the generated connection between the ATM terminal 10 ₁ and the ATM terminal 10, it is assumed that the data communication such as moving image is being performed. Here, the cell transmission statistics collection unit 134 of the ATM interface card 13 counts the transmission speed related to VCC during data communication, that is, the number of bytes per second in cell units, and the like.

Thereafter, the connection control processing section 124
Reads the total value of the transmission statistics obtained by the cell transmission statistics collection unit 134 and evaluates communication parameters such as the cell speed. In evaluating the communication parameters, the communication parameters of the currently communicating connection are compared with the communication parameters obtained from the aggregated value based on the transmission statistics, and the communication parameter obtained from the aggregated value is excessively larger than the communication parameter of the currently communicating connection. If it is, that is, if the value exceeds the range of communication parameters determined in advance by the user side, a new connection is generated using an arbitrary ATM layer service category, for example, CBR. And if a new connection is created,
Data transmission is performed by switching from the previous connection to the new connection.

Therefore, according to the configuration of this embodiment, transmission statistics are totaled for each cell during data communication, communication parameters are evaluated based on the totaling result, and problems occur in terms of communication quality and efficiency. In some cases, a new connection is created, and after this new connection is established, the connection is switched to the new connection and data communication is performed.
A connection is appropriately generated based on a change in the amount of data during communication, and data can be stably communicated while maintaining required quality. (Third Embodiment) FIG. 4 is a block diagram showing an embodiment of a network data communication system according to the third aspect.

In this embodiment, an ATM network is provided between Ethernet terminals at both ends, and data is transmitted in a frame format.
An object of the present invention is to realize a data communication system that is considered to be directly connected by M.

This Ethernet is a CSMA / CD system, in which all terminals are connected to one transmission cable.
This is a data communication system in which this transmission cable is transferred in a data frame format as a common data transmission path, and can be said to be a connectionless system similar to a datagram of the wide area packet communication technology.

Hereinafter, a specific description will be given with reference to FIG.
A Ethernet terminal such as 20 _1, 20 ₂ is a personal computer in the drawing, for convenience of explanation, 20
₁ transmitting terminal, 20 ₂ to the receiving terminal. This CS
The MA / CD protocol is a physical interface,
Medium access control (MAC) and logical link control (L
LC), which corresponds to a range between layer 1 (physical layer) and layer 2 (data link layer) of the OSI reference model, and is a function necessary for packet transmission. Therefore, these terminals 20 _1, 20 ₂ has a programming interface that handles pseudo ATM connection for implementing the protocol described above,
It has a function to embed and transmit an ATM signaling message in the data frame format.

As shown in FIG. 5, the data frame format includes an Ethernet header and an IP (Internet Protocol).
) Header, TCP (Transmission Control Protocol)
), Q. 2931 message and FCS (frame check sequence). 29
31 is Q.31 which is a layer 3 protocol of N-ISDN.
931 and Q.I. 933 based on B-ISDN with messages related to connection setup / release.

[0049] Each of 21 ₁ and 21 ₂ extracts an ATM signaling message from the data frame format.
Frame for performing ATM signaling to the network side
It is a bridge that has an ATM conversion function. A plurality of ATM exchanges 22 ₁ , 22 ₁ are connected between these bridges 21 ₁ , 21 _2.
An ATM network 22 composed of ₂ ,..., 22 _n is connected.

As shown in FIG. 6, the bridges 21 ₁ and 21 ₂ include an Ethernet port 211 for receiving a data frame from the Ethernet terminal, a data storage memory 212 for storing the received data frame, A program memory 213 for storing programs for processing and ATM conversion processing;
The received data in the data storage memory 212 is analyzed, rejected, or internally processed,
Forward to the M port 214, It comprises a data processing control unit 215 having a microprocessor or the like that decodes the 2931 message and generates VCC.

Next, the operation of the above-described network data communication system will be described. When transferring data to the reception side terminal 20 ₂ from the transmitting terminal 20 _1, the transmission side terminal 20 _1, I in the data frame as shown in FIG. 5
Q. of the TU-T Recommendation. 2931, an ATM signaling message is provided therein, and the ATM signaling message is embedded therein and transmitted in a frame format.
Generally, ATM (User Network) is used for ATM signaling.
rk Interface) signaling and NNI (Network Network)
ork Interface) signaling. Currently, the signaling of UNI is based on ITU-T Recommendation Q.2. 29
It is common to use 31. Q. Normally, the message 2931 is exchanged between the ATM terminal and the ATM exchange. In this embodiment, Q.2931 is included in the TIP / IP information of the data frame output from the terminal connected to the Ethernet. Insert the 2931 message. At this time, Q. It is assumed that a TCP port number is assigned for 2931 message identification. The destination address written in the frame is addressed to the bridge to which the Ethernet terminal is connected.

[0052] In other words, the transmitting terminal 20 _1, ATM API (Application from the application task
Programming Interface) When a transmission request for another terminal is generated through an API equivalent to Q.
A frame including the 2931 message is transmitted.

[0053] Here, the bridge 21 ₁ via the Ethernet port 211 Q. When a data frame including the 2931 message is received, the data frame is temporarily stored in the data storage memory 212. Here, the data processing control unit 215
Analyzes the contents of the data frame according to the program in the program memory 213, and It extracts the 2931 message and performs ATM signaling to the ATM network 22.

[0054] Here, when the ATM network 22 generates a VCC based on the request of the transmitting terminal 20 _1, Q.
The response message of the 2931 message is returned. The transmitting terminal 20 _1, Q. When a response message of the 2931 message is returned, it is determined that a virtual ATM connection has been created, and data communication is performed using the virtual connection. At this time, a specially assigned TCP port number is used, and VPI / VCI is used as an identifier.

[0055] bridge 21 ₁ examines the TCP number,
If it is determined that the data is data using a virtual ATM connection, VPI / VCI is extracted and the corresponding output VPI /
Convert to VCI, AAL (ATM Adaptation Layer) 5
And the predetermined VCC of the ATM network 22
Output to

[0056] Thus, the bridge 21 ₂ side, AT to reverse
After receiving data from the M network side, the virtual AT
Q. for M connection and for Ethernet terminals. 2931 If you must deliver the message, the Ethernet terminal 20 ₂ by processing the frame
Deliver to.

Therefore, according to the configuration of the above-described embodiment, even when both the transmitting terminal and the receiving terminal are Ethernet terminals, frame-A
By performing TM conversion or ATM conversion-to-frame conversion, a VCC is explicitly generated for an intermediate ATM portion and data is transferred, so that communication quality of data can be guaranteed. (Fourth Embodiment) FIGS. 7 and 8 are diagrams illustrating an embodiment of a network data communication system according to the fourth aspect.

This embodiment is a data communication system of a network for performing data communication in a packet format. When a transmitting terminal has a connection-type transport layer equivalent protocol, the flow control in the protocol is appropriately performed. To run.

In general, the transport layer (fourth layer of the OSI reference model) provides network-independent end-to-end connection and processing services, and the transport protocol transmits application data. It breaks down into ordered packet formats, manages the transmission of these packets, and provides ordered, non-overlapping or lost data delivery.

At the level corresponding to the transport layer, there are two main protocols, ie, TCP and UDP, of which TCP is connection-type communication.
It is suitable for establishing a virtual circuit (virtual circuit) prior to communication and transmitting a large amount of data continuously. Since the TCP supports a wide range of upper layer data transmission, it has a number of ports for specifying the upper layer.

Accordingly, since the transmitting side ATM terminal 31 ₁ has a large number of ports, the first TCP
The packet format is such that a header portion is added with an acknowledgment number ACK, a window WNDW for performing flow control, and other necessary control information in addition to a source address and a port number, a destination address and a port number.
Transmitting the ATM terminal 31 ₂ of the receiving side through M network or general the ring network 32 of the internetwork, and the like.

[0062] Incidentally, the transmission side ATM terminal 31 ₁ as described above is the software task configuration as shown in FIG. That is, the transmitting side ATM terminal 31 ₁ is divided into a user side and a kernel side in terms of task configuration, and the user side monitors the congestion state of the application task 33 and the network 42 applicable to each user's request. A network monitoring task 34 is provided on the kernel side, while basic software for communication, that is, T
CP task 36, IP task 37, MAC related to medium access control MAC which is one of the sub-layers of the data link layer
A driver 38 and the like are provided.

The network monitoring task 34 includes a window collection unit for periodically collecting transmission window numbers for each TCP connection, a window holding unit for holding the transmission window numbers collected by the collection unit in time series, A congestion presence / absence determining means for determining the presence / absence of congestion based on the history of the held transmission window numbers, and an IP MTU (Maximum)
Transmission size variable control means for reducing the size of the transmission unit is provided.

Next, the operation of the above-described network data communication system will be described. Now, when communicating in packet form from the application task 33 to the other receiving terminal 31 _2, it passes the data from the application task 33 to TCP task 36, further passes from the TCP task 36 to IP task 37. This IP task 37
Are transmitted via the MAC driver 37.

At this time, the network monitoring task 34
Periodically captures the transmission window number for each TCP connection held by the TCP task 36, stores the transmission window number as an internal variable in time series, and determines the progress of the transmission window number from the history of the transmission window number. I do. That is, when it is determined that the progress of the transmission window number is slow, it is determined that congestion has occurred, and the IP MTU size of the corresponding TPC connection is reduced.
Reduce the effects of congestion. Conversely, when it is determined that the progress of the transmission window number is smooth, the IP MTU size of the TCP connection is increased.

Therefore, according to the data communication method of the above-described embodiment, the transmission window numbers for each TCP connection are stored in chronological order, and the progress of the transmission window numbers is determined from the history of the transmission window numbers. Therefore, even when the network is an ATM, the I
It is possible to reduce the packet loss rate of P packets. (Fifth Embodiment) An embodiment of a network data communication system according to claim 5 will be described. Since the configuration of this embodiment is substantially the same as that of FIGS. 4 to 6, the description will be made using the configurations of FIGS. 4 to 6.

In this embodiment, in a data communication system of an ATM network in which an Ethernet terminal is connected to both ends, a frame transmitted from an Ethernet terminal on the transmission side is used for bandwidth reservation such as RSVP (Resource Reservation Protocol: Resource Reservation Internet Protocol). In this method, a message is embedded and a bandwidth reservation is made in advance.

This Ethernet is of the CSMA / CD system, in which all terminals are connected to one transmission cable,
This is a data communication system in which this transmission cable is transferred in a data frame format as a common data transmission path, and can be said to be a connectionless system similar to a datagram of the wide area packet communication technology.

As shown in FIG. 4, the configuration of this embodiment is such that an Ethernet terminal 20 such as a personal computer is used.
_1, the bridge 21 ₁ having a 20 ₂ a frame -ATM conversion function that performs the ATM signaling, respectively, 21 ₂
Is connected between the bridges 21 ₁ and 21 _2.
Network 22 is connected.

[0070] These terminal 20 _1, 20 _2, CSMA /
Pseudo ATM for realizing CD protocol
It has a programming interface for handling connections, and has a function of embedding and transmitting ATM signaling messages in a data frame format. This data frame format includes an Ethernet header, an IP (Internet Protocol) header, a TCP
(Transmission Control Protocol); 2931 message and FCS (frame check sequence). 2931 has N-ISD
N, which is a layer 3 protocol of Q.N. 931 and Q.I. 9
33 to the base, other Meseji on setting and release of the connection as B-ISDN, the bridge 21 _1, 21 _2, embeds the band reservation message RSVP, etc. is sent from the terminal, as shown in FIG. 6 An Ethernet port 211 for receiving incoming data frames, a data storage memory 212 for storing received data frames, a program memory 213 for storing programs for received data processing and ATM conversion processing, and an ATM port 214. The received data in the data storage memory 212 is analyzed, rejected,
It performs internal processing, forwards received data to the ATM port 214, Decrypt 2931 message and V
It is configured by a data processing control unit 215 having a microprocessor or the like that generates a CC.

Next, the operation of the above-described network data communication system will be described. Sending terminal 20 ₁
Is the ITU-T in a data frame as shown in FIG.
Q. of the recommendation. The 2931 is provided, the bridge 21 ₁ data frame having the ATM signaling messages to
Send to

[0072] Here, the bridge 21 ₁ via the Ethernet port 211 Q. When a frame including the 2931 message is received and stored in the data storage memory 212, the data processing control unit 215 sets the program memory 2
13 to analyze the contents of the frame data according to the program of Q.13. 2931 message is extracted, ATM signaling is performed to the ATM network 22, and a virtual ATM
It generates a connection and is connected to the receiving terminal 20 ₂ performs data communication using the virtual connection.

By the way, during the data communication, Q. transmitting terminal 20 ₁ is in the data frame ATM on 2931
Other signaling messages, when an embedded band reservation message such as RSVP, bridge 21 _1,
When the Ethernet-ATM conversion is performed, a request in the bandwidth reservation message is analyzed, and a process of generating a VCC of the bandwidth is performed according to the request. That is, the bridge 21 _1, when the band reservation message such as RSVP flows, to determine the service parameters data virtual channel connection LAN emulation, the LA
This guarantees communication quality while using N emulation.

[0074] Therefore, according to the data communication system of the above-described embodiments, without using a router, when the bridge 21 ₁ flows bandwidth reservation message of RSVP, etc. from the transmitting terminal 20 _1, the LAN Emulation Since the service parameters of the data virtual channel connection are determined and the data frame is transmitted based on the LAN emulation, the communication quality can be guaranteed. (Sixth Embodiment) FIG. 9 is a block diagram for explaining an embodiment of a network data communication system according to the sixth aspect.

This embodiment is capable of reserving bandwidth and other resources, and furthermore, in a data communication system of a network consisting of an ATM switch and an ATM terminal which performs reception control, a communication system between the ATM switch and the ATM terminal. The purpose of the present invention is to monitor the amount of data actually flowing in the ATM exchange after the traffic contract, and to reduce the allocated bandwidth and to efficiently use the resources of the exchange when only a much smaller amount of data flows than the contract.

In the figure, 41 ₁ , 41 ₂ ,.
, An AT comprising a plurality of ATM exchanges 42 ₁ , 42 ₂ ,... Between the ATM terminals 41 ₁ , 41 ₂ ,.
An M network 42 is interposed.

The ATM terminals 41 ₁ , 41 ₂ ,... Generate a virtual connection and execute a release process after the data transfer is completed. It comprises an ATM interface card 44 for grasping the state and the like.

The connection creation / release processing unit 43
Are a program memory 431 for storing a processing program for performing connection generation (setting) control, connection release control, and other necessary processing control; a main memory or an external storage device 432 for storing moving image data and the like; It comprises a buffer memory 433 for storing data, a connection control processing unit 434 such as a microprocessor for reading a necessary processing program from the program memory 431 and executing connection generation control.

On the other hand, the ATM interface card 44
Is a SAR (Segmentation And Reassembly) unit 4 that outputs, in addition to functions such as cell division and assembly and header translation, connection information such as destination and bandwidth reservation to the header of the cell.
41, a physical layer unit 442 for storing a plurality of divided cells and outputting frame format data, an optical-electrical conversion unit 443, and signaling to the ATM network 11 to perform VC
It comprises a cell transmission statistics collection unit 444 for observing the transmission rate for the VCC after establishing C.

The connection generation / release processing unit 43
And the ATM interface card 44 are connected by a system bus 45. In the ATM network including the ATM terminal as described above, the ATM terminal 41 ₁
Prior to performing data communication with another ATM terminal as a communication partner, signaling performs signaling to set up a connection.

On the other hand, each ATM switch 42 _i (42 ₁ , 4
2 ₂ , 42 ₃ , 42 ₄ ,...) Are configured as shown in FIG. The ATM switch 42 _i includes a receiving port to d for receiving data frame format, and converts the received data frame (light) into electric signals by these receiving ports to d, the clock from the electrical signal .., And an SDH (Synchronous Digital Hierarchy) using the extracted clock.
..) For extracting ATM cells from the frame and outputting header information, and a traffic table 423 for storing parameters as shown in FIG.
A traffic observing section 424, which extracts destination information such as a destination port and new VPI / VCI information by referring to the traffic table 423 based on the header information and adds it to the head of the cell information, is provided. Therefore, each cell extracting unit 422 adds destination information to the head of the cell information and writes the destination information to the shared memory buffer 425.

Each ATM switch 42 _i checks the destination information of the data written in the shared memory buffer 425 and outputs the data to an appropriate port.
25a, a framer 426 for storing a plurality of cells and outputting the SDH frame as an SDH frame, a transmitter 427 for converting the SDH frame into an optical signal and outputting the same, and resource control and other necessary while referring to the traffic table 423 And a management unit 428 for performing various control management.

Note that the “set value” of the traffic table 423 is set with the number of communication cells per unit time set at the time of connection setting. The "actual measurement maximum value" measures the number of communication cells per unit time when actual communication starts after connection setting, and stores the maximum value of the number of communication cells per unit time. This measured maximum value is the set value of 50
When the percentage becomes less than 100 times in the unit time, it is determined that the report is over-reported, and the allocated bandwidth is reduced.

Next, the operation of the above-described network data communication system will be described. The connection control processing unit 43 of the ATM terminal 41 ₁ on the transmitting side performs signaling according to the processing program of the program memory 431 to generate VCC and performs data communication. At the time of the signaling, the ATM terminal 41 ₁ communicates with the ATM switch 42 _i . Between the ATMs
Telephone exchange 42 _i, and registers the agreement regarding traffic in the traffic table 423, generates a VCC to allocate resources to meet the band was in request traffic contract, for data communication.

Thereafter, the management unit 4 of the ATM switch 42 _i
Reference numeral 28 monitors the amount of cell data flowing on the VCC during data communication. That is, the management unit 428 refers to the set value of the traffic table 423 and the measured maximum value of the number of communication cells per unit time for the amount of cell data flowing on the VCC, and the measured maximum value is 50% or less of the set value. When the number of times exceeds 100 times in the unit time, it is determined that the report is excessive, and the bandwidth allocated in the own ATM exchange is reduced.
Notify _i that bandwidth has been reduced.

Although the above embodiment has been described with reference to an ATM network, a general communication network capable of resource management may be used. Therefore, according to the data communication method of the above-described embodiment, when the exchange has a function of performing admission control, when the data amount during the actual data communication is much smaller than the contracted traffic amount, a predetermined value is set. Since the allocated bandwidth is reduced, wasteful traffic can be excluded.
The opportunity of CC generation can be increased, and the resources of the exchange can be efficiently utilized. (Seventh Embodiment) FIGS. 12 and 13 are block diagrams for explaining an embodiment of a network data communication system according to the seventh aspect.

In this embodiment, in a data communication system of an ATM network, when a traffic contract is made, the ATM exchange side notifies the transmitting side ATM terminal of the burst tolerance due to restrictions on buffer memory capacity and the like.
The terminal uses the MTU (Maxi
mum Transfer Unit).

Specifically, the upper system 51 sends an IP
Upon receiving the packet frame, the transmitting ATM terminal 52
Concludes a traffic contract with the ATM switch 53 and performs signaling. Here, when the ATM switch 53 generates the VCC based on the traffic contract request, the transmitting ATM terminal 52 divides the cells based on the IP packet according to the MTU, and transmits the data to the partner ATM terminal through the VCC.

At this time, the transmitting ATM terminal 52 transmits
The packet is divided into n cells according to the MTU-sized IP packet and transmitted without knowing the burst tolerance m of the ATM switch 53.

As a result, in the ATM switch 53, the relationship of n> m is satisfied, so that (nm) cells are left, and (nm) cells are discarded. As a result, The IP packet will not arrive at the destination ATM terminal.

Therefore, the ATM switch 53 transmits to the transmitting side AT
When the VCC is set, the M terminal 52 is notified of the burst tolerance m. Here, when the transmitting ATM terminal 52 receives the burst tolerance m, it temporarily stores it in the buffer memory, and based on the burst tolerance m, the MTU.
The size is changed, the size of the IP packet is determined according to the MTU, and the IP packet is converted into a cell based on the size and transmitted.

Therefore, according to the above-described embodiment, the transmitting ATM terminal 52 determines the MTU based on the burst tolerance of the ATM switch 53 and converts the IP packet into a cell, and transmits the IP packet. It is possible to prevent the loss of the IP packet and the cell due to being too large, and the IP packet can be surely transmitted to the counterpart ATM terminal in the form of a cell. (Eighth Embodiment) FIG. 14 is a block diagram for explaining an embodiment of a network data communication system according to the eighth aspect.

This embodiment relates to a data communication system of a data transmission network in which a plurality of industrial controllers and computers are connected, and receives a data frame occupying a large band in a burst like data for file transfer. In this case, the data for file transfer is delayed, and the delay time is used to increase the number of data between other controllers.

[0094] Specifically, as shown in FIG. 14, for example, occupies the plurality of Ethernet terminals 61 _1, 61 _2, 61 ₃ which functions as an industrial controller, a burst manner large bandwidth as file transfer data a node 62 for delaying the data frame or the like, and an Ethernet hub 63 to concentrator processes the Ethernet terminal 61 _1, 61 _2, 61 ₃ and node 62 is provided.

[0095] The Ethernet hub 63, a plurality of Ethernet terminals 61 _1, 61 _2, 61 ₃ and node 62
These ports are connected to a hub unit 633 via a physical layer dependent transmitting / receiving unit 631 and a MAC (Media Access Control) unit 632, respectively. ing.

Next, the operation of the data communication system of the network having the configuration shown in FIG. 14 will be described. Now, the data sent from the Ethernet terminal 61 _1, received in the corresponding port 1, the physical layer dependent transceiver 631 and M
The data is sent to the hub unit 633 via the AC unit 632. When the received data is broadcast data, the hub unit 633 sends the data to the port 2 or 3. If the data is unicast data, the port number of the TCP is checked to determine whether the data is bulk transfer data such as file transfer. When it is determined that the data is bulk transfer data, the data is sent to port 4. The data received from port 4 is output after being delayed by the time determined by internal register 621 in node 62. For example, 1Mb
In the case of a 10 Mbps Ethernet with a memory capacity of it, a time delay of 1 Mbit / 10 Mbps = 100 ms. Then, the internal shift register 621
Is returned to the hub unit 633 again and sent to the required port 2 or 3 based on a predetermined destination. On the other hand, as a result of inspecting the TCP port number in the hub unit 633, if it is determined that the data is not bulk transfer data, the data is sent to a predetermined destination node as it is.

As a result, for bulk transfer data,
Output is performed with an artificial delay, flow control by TCP window control works, the transmission speed is reduced, and the risk of data transfer of other emergency messages being stopped for a long time in bulk transfer in the network can be prevented.

Referring to FIG. 15, for example, FIG.
When the inter-control data is transmitted via the Ethernet hub 63 as shown in (a), and when the file transfer indicated by the △ mark is performed as shown in FIG. Therefore, the emergency message cannot be transferred to the node that needs it.

Therefore, as shown in FIG. 11C, the hub unit 633 sends the file transfer data to the node 62 and delays it by a predetermined time, so that the inter-control data is transferred within the delay time and the emergency message is transmitted. Enable transfer.

Therefore, according to the data communication system of the above-described embodiment, the line coming out of each controller is connected to the hub 6.
3 is provided, and a node 62 for increasing the delay time is provided at one port of the hub 63. When a data frame occupying a large band in a burst like data for file transfer is received, the data frame is expanded. Since the data frame is sent back to the desired destination after returning to the hub 63 again through the node 62 having a delay time,
By intentionally increasing the delay time between the end nodes required for file transfer and lowering the transfer rate, data communication can be performed without interruption between controllers.

Although the above embodiment uses an Ethernet hub for a data transmission network such as a control LAN, the present invention can be similarly applied to a case where this Ethernet switch is used. Further, although the number of ports is four, the present invention can be implemented using an arbitrary number of ports and an arbitrary number of hubs. (Ninth Embodiment) FIG. 16 is a block diagram for explaining an embodiment of a network data communication system according to the ninth embodiment.

This embodiment relates to a data communication system of a data transmission network in which a plurality of industrial controllers and computers are connected, wherein a delay buffer module is provided inside an Ethernet hub or an Ethernet switch. When a data frame occupying a large band in a burst, such as file transfer data, is received as in FIG. 14, this file transfer data is delayed,
This method uses the delay time to increase the number of other inter-controller data.

[0103] Specifically, as shown in FIG. 16, a plurality of Ethernet terminals 61 _1, 61 _2, 61 _3, 61 ₄ that functions as, for example, industrial controllers, these terminals 6
1 _1, 61 _2, 61 _3, 61 ₄ made from an Ethernet hub 63 to concentrator process, of which, an Ethernet hub 63 is Ethernet terminal 61 _1, 61 _2, 61 _3, 6
1 ₄ corresponding port 1, 2, 3, 4 respectively provided in the hub unit 6 respectively Korare ports 1, 2, 3 and 4 via the physical layer dependent transceiver 631 and MAC unit 632
33 are connected. The hub unit 633 is provided with a buffer (shift register) 634 for delaying a data frame or the like occupying a large band in a burst like data for file transfer.

Next, the operation of the above embodiment will be described. Now, the data sent from the Ethernet terminal 61 _1, received in the corresponding port 1, the hub unit 6 via the physical layer dependent transceiver 631 and MAC unit 632
33. When the received data is broadcast data, the hub unit 633 transmits the data to the port 2 or 3 or 4. If the data is unicast data, the port number of the TCP is checked to determine whether the data is bulk transfer data such as file transfer. When it is determined that the data is bulk transfer data, the data is sent to the internal shift register 634. Here, the data is sequentially shifted every predetermined time, output after a predetermined delay time, returned to the hub unit 633 again, and sent to a predetermined destination node.

When the hub unit 633 checks the TCP port number and determines that the data is not bulk transfer data, it sends the data as it is to a predetermined destination node. As a result, the bulk transfer data is output with an artificial delay, the flow control by TCP window control works, the transmission speed becomes slow, and the data transfer of other emergency messages in the bulk transfer in the network is long. It is possible to prevent the danger of time stoppage.

Therefore, according to the data communication system of the above-described embodiment, the line from each controller is connected to the hub 6.
3, a buffer 634 for creating a predetermined delay time is provided in the hub 63. When a data frame occupying a large band in a burst like data for file transfer is received, the data frame is converted to a large delay time. After returning the data frame to the hub 633 again through the buffer 634, the data frame is sent to the desired destination.
By intentionally increasing the delay time between the end nodes required for file transfer and lowering the transfer rate, data communication can be performed without interruption between controllers. Although the number of ports is four, the present invention can be implemented using an arbitrary number of ports and an arbitrary number of hubs.

[0107]

As described above, according to the present invention, the following various effects can be obtained. In the invention of claim 1, U
After the connection is generated using the BR service category, the data is transmitted, and after grasping the status of the network, a new connection is generated and data communication is performed.
Even when the communication parameters are not known in advance, data communication can be performed according to the transmission capability.

According to the second aspect of the present invention, data communication can be performed under an optimal connection while sufficiently coping with a change in the amount of transmission data. According to the third aspect of the present invention, data communication can be performed between terminals that handle data in a frame format while maintaining ATM communication quality.

According to the fourth aspect of the present invention, since the IP MTU size of the TCP connection is changed in accordance with the progress of the window number, the packet loss rate of IP packets during congestion can be reduced.

According to a fifth aspect of the present invention, when a bridge is interposed between a transmission side Ethernet terminal and an ATM network and data of a frame format is communicated, the bridge, when there is a bandwidth reservation message in a frame, the content of the reservation. , The data communication can be performed while guaranteeing the communication quality of the network.

According to a sixth aspect of the present invention, when the actual data amount is smaller than the contract with the transmitting side terminal, the ATM exchange reduces the allocated bandwidth and notifies the transmitting side terminal that
The resources of the ATM exchange can be used efficiently.

According to a seventh aspect of the present invention, the transmitting-side ATM terminal uses M based on the burst retransformer of the ATM exchange.
Since the TU size is variable, it is possible to prevent IP packets from being discarded. According to the invention of claims 8 and 9, even when a certain terminal continuously transfers a large amount of data, another terminal can easily use the network.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an embodiment of a data communication system of a network according to claim 1.

FIG. 2 is a view for explaining the relationship between connection generation and data transmission.

FIG. 3 is a view for explaining a data communication system of a network according to claim 2;

FIG. 4 is a configuration diagram showing an embodiment of a network data communication system according to claim 3.

FIG. 5 is a configuration diagram of a frame handled by the network data communication method according to claim 3;

FIG. 6 is a diagram showing a specific configuration example of a bridge shown in FIG. 4;

FIG. 7 is a configuration diagram showing an embodiment of a data communication system of a network according to claim 4.

FIG. 8 is a view for explaining a task configuration of the transmitting terminal shown in FIG. 7;

FIG. 9 is a configuration diagram showing an embodiment of a data communication system of a network according to claim 6;

FIG. 10 is a diagram showing a specific configuration example of the ATM exchange shown in FIG. 9;

11 is an exemplary view for explaining an example of a data string stored in the traffic table shown in FIG. 10;

FIG. 12 is a configuration diagram showing an embodiment of a network data communication system according to claim 7.

FIG. 13 is a view for explaining an example of changing the MTU size in FIG. 12;

FIG. 14 is a configuration diagram showing an embodiment of a network data communication system according to claim 8.

FIG. 15 is a view for explaining the operation of the data communication system shown in FIG. 14;

FIG. 16 is a configuration diagram showing an embodiment of a network data communication system according to claim 9.

FIG. 17 is a diagram showing a conventional ATM network configuration.

FIG. 18 is a diagram showing a conventional Ethernet network configuration.

[Explanation of symbols]

10 ₁ , 10 ₂ , 31 ₁ , 31 ₂ , 41 ₁ , 41 ₂ , 5
2 ... ATM terminal 11,22,42 ... ATM network _{11 1, 11 2, 42 1} ,, 53 ... ATM exchange 12 ... Connection generation and release processing section 13 ... ATM interface card 134 ... cell transmission statistics collection unit 20 _1, 20 ₂ , 61 ₁ , 61 ₂ , Ethernet terminal 21 ₁ , 21 _2, Bridge 32, Network 34, Network monitoring task 51, Host system 62, Node 63, Ethernet hub 633, Hub part 634, Delay buffer

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Mitsuko Kobayashi 1 Toshiba-cho, Fuchu-shi, Tokyo Inside the Fuchu plant of Toshiba Corporation

Claims (9)

[Claims] In a data communication system of a network for communicating data between ATM terminals through an ATM network having a plurality of ATM exchanges, if communication parameters are not known in advance, the transmitting-side ATM terminal is connected between the ATM exchanges. UBR (Unspecifi-ed Bit Rat
e) first connection generation means for generating a first connection using a service category, and after generating the first connection, data is actually divided into cells and transmitted, and transmission statistics are totaled for each cell. The communication parameters are determined based on the transmission statistics collecting means and the aggregated transmission statistics, and CBR (Co
nstant Bit Rate) or VBR (Variable Bit Rate)
) To create a new second connection
A data communication method for a network, wherein the data communication method is performed by switching to the second connection. 2. A data communication method for a network in which data is transmitted between ATM terminals through an ATM network having a plurality of ATM exchanges. In a data communication system, a transmitting-side ATM terminal performs transmission statistics on a cell-by-cell basis during data communication after connection creation. Transmission statistics collecting means for compiling the communication parameters obtained from the collected transmission statistics and the communication parameters of the currently communicating connection, and the communication parameters obtained from the transmission statistics are obtained from the communication parameters of the currently communicating connection. Connection processing control means for generating a new connection based on communication parameters obtained from transmission statistics when the parameter value exceeds a desired parameter value range, and switching to the newly generated connection to perform data communication. Network data communication Method. 3. A plurality of ATs between Ethernet terminals at both ends.
In a data communication system of a network in which an ATM network having an M switch is provided and data communication is performed in a frame format, a bridge is provided between each of the Ethernet terminals and the ATM network.
ol Protocol) / IP (Internet Protocol) and transmits the ATM signaling message by embedding the ATM signaling message in the data frame. Each of the bridges extracts the ATM signaling message from the received data frame, A
A data communication system for a network, wherein signaling is performed to a TM network to perform data communication in a frame format. 4. A data communication system for a network having a connection-type transport layer equivalent protocol and performing flow control using a window at a transmitting terminal.
When performing data communication with the receiving terminal via the task, the TCP task periodically determines the progress of the transmission window number from the history of the transmission window number for each TCP connection possessed by the TCP task. A network data communication system comprising a network monitoring task for changing a size of an IP MTU (maximum transmission unit) of a connection. 5. A plurality of ATs between Ethernet terminals at both ends.
An ATM network having an M switch is provided, and in a data communication system of a network for communicating data in a frame format, a bridge is provided between each of the Ethernet terminals and the ATM network.
ol Protocol) / IP (Internet Protocol) and embeds an ATM signaling message and a bandwidth reservation message in a data frame and transmits the data frame. Each of the bridges extracts a bandwidth reservation message from the received data frame. A data communication method for a network, wherein the ATM signaling is performed to generate a VCC according to the request reservation content of the bandwidth reservation message. 6. In a data communication system for a network comprising a terminal and an ATM switch which performs reservation control, wherein said band and other resources can be reserved, said ATM switch performs a data contract after a traffic contract is made between a transmitting terminal. Monitors the amount of data flowing through the VCC during communication, and when the contracted amount is equal to or less than a predetermined amount and continues for a predetermined number of times per unit time, reduces the allocated bandwidth and notifies the transmitting side terminal of the bandwidth reduction. A data communication system for a network, comprising a notifying unit. 7. In a data communication system of a network in which an ATM network having a plurality of ATM switches is arranged between ATM terminals, said ATM switch notifying a transmitting ATM terminal of burst tolerance, and transmitting from said ATM switch. MTU size is determined on the basis of the received burst tolerance, and this determined M
A transmitting-side ATM terminal that determines the size of an IP packet according to a TU, divides the cell, and transmits the data, and a data communication method for a network. 8. A data communication system for a network in which a plurality of devices transmit and receive data via a network, comprising: an Ethernet hub or an Ethernet switch for concentrating data lines output from the plurality of devices on the network. A node for generating a delay time, wherein the Ethernet hub or the Ethernet switch receives data occupying a large bandwidth from a certain device, inputs the data to the node, delays the data, and then returns to the Ethernet again. Hub or Ethernet
A data communication system for a network, wherein the data is returned to a switch and sent to a device of a desired destination, and data communication between other devices is enabled during the delay time. 9. A data communication method for a network in which a plurality of devices exchange data via a network, comprising: an Ethernet hub or an Ethernet switch for concentrating data lines output from the plurality of devices on the network. The Ethernet hub or the Ethernet switch has a buffer for creating a delay time, and when receiving data occupying a large band from a certain device, after delaying the data by the buffer, the Ethernet hub or the Ethernet switch has a desired destination. A data communication method for a network, wherein data is transmitted to a device and data communication between other devices is enabled during the delay time.