JP3247747B2 - ISDN data terminal equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ISDN data terminal apparatus for transmitting data using bearer services in ISDN packet switching mode and frame mode.

[0002]

2. Description of the Related Art When various data terminals communicate with each other using ISDN, communication may not be possible if the network is congested.

For example, when a data terminal device makes a call in the circuit switching mode, if the network is congested, there is a case where a call cannot be made to a communication partner due to a busy line. Also, if the network is congested during communication in the packet switching mode, the communication channel may be forcibly disconnected and communication may not be possible. Furthermore, during communication in frame mode,
When the network is congested, a transmission frame may be lost in the network and transmission data may be lost.

[0004]

As described above, conventionally,
When data is transmitted by ISDN, there is a problem that communication is hindered when the network is congested.

[0005] It is an object of the present invention to provide an ISDN data terminal device which solves the above-mentioned problems and minimizes communication problems due to network congestion.

[0006]

To this end, the present invention provides
In an ISDN data terminal device provided with two data transmission means of a packet switching mode and a frame mode, at the start of communication, means for starting data transmission with a communication partner in the frame mode, and means for detecting network congestion Means for starting data transmission in the packet switching mode while maintaining the connection for data transmission in the frame mode when network congestion is detected; and Means for increasing the amount of data transmission according to the mode.

[0007]

Since data transmission is started in the frame mode first, data transmission can be performed in a short time by effectively utilizing high throughput. If the network becomes congested during the data transmission, a packet switching mode is added, the amount of data transmission in the frame mode is reduced, and most of the data is transmitted in the packet switching mode. As a result, even if the network is congested, the remaining data can be transmitted without being incapable of communication, and communication trouble due to network congestion can be minimized.

[0008]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a data terminal apparatus according to one embodiment of the present invention. In the figure, an input unit 1 is for inputting data to be transmitted, and an output unit 2 is for outputting received data. For example, when the data terminal device is a terminal device that transmits and receives image information, the input unit 1 is a scanner device, and the output unit 2 is equivalent to a plotter device. The storage unit 3 stores various control data necessary for the communication operation, and accumulates transmission / reception data as necessary.

[0010] The ISDN communication unit 4 is connected to the ISDN via a circuit terminating device (not shown) and communicates with a communication partner. The operation display unit 5 displays various information such as the operation state of the apparatus while the operator performs various operations. The system control unit 6 is a macro computer that monitors and controls the above units.

FIG. 2 shows a first embodiment of the communication operation of the above data terminal device. That is,
In the present embodiment, the data terminal device performs a predetermined outgoing / incoming operation in a bearer service in a normal packet switching mode. Thereby, a predetermined data transfer connection with the communication partner device is set.

The ISDN packet-switched vera services include a virtual call bearer service and a permanent virtual circuit bearer service.
In this embodiment, for example, a virtual call bearer service is used. In this virtual call bearer service, CCITT Recommendation X. 25 and X. In this case, the communication is performed in accordance with No. 31.

In this case, as shown in FIG.
Each of the data terminal devices 11 is connected to a packet handler 13 via an exchange 12 in the ISDN.
Then, the packet switching function of the packet handler 13 forms a logical channel between the two data terminal devices 11. Each data terminal device 11 sets a connection for data transfer using the logical channel (process 101).

The data terminal device starts data transmission through the set connection (process 102). After this,
It monitors whether a CI (disconnection instruction) packet or an SI (restart instruction) packet is received (processing 10).
3). If not received (N in process 103), the remaining amount of transfer data is checked (process 104, process 10).
4N), the monitoring is continued (to process 103).

By the way, during such communication, the communication channel may be disconnected by the network at the time of forced communication. In packet switched mode, if this communication channel is disconnected,
A CI packet or SI packet is transmitted from the ISDN to the terminal device side.

In this embodiment, the data terminal device receives the CI packet or the SI packet (step 103).
Y), the cause of disconnection of the communication channel is determined. An information field indicating the cause of disconnection is formed in the CI packet and the SI packet, and the cause of disconnection is determined based on the information (process 105).

The cause of the disconnection in this case includes, for example, a disconnection operation on the partner terminal device side, network congestion, and the like. Now
If the cause of the disconnection is congestion of the network (Y in process 105), the data transfer is interrupted and the set data transfer connection is released (process 106).

Next, the data terminal device executes a predetermined transmission / reception operation with respect to the same destination by the bearer service in the frame mode.

The vera service in the frame mode uses a layer 2 data frame as a transfer unit, and the ISD
In the case of N, there are a frame relay service and a frame switch service. In this embodiment, for example, a frame relay service is used.

In this case, as shown in FIG.
One data terminal device 11 is connected to an exchange 12 in the ISDN network.
Is connected to the frame relay handler 14 via the. The frame relay function of the frame relay handler 14 forms a logical channel between the two data terminal devices 11. Each data terminal device 11 sets a new data transfer connection by using the logical channel (process 107).

The data terminal restarts data transfer through the set data transfer connection (step 10).
8). Thereafter, the remaining amount of transfer data is monitored (step 109).
When the transfer data is completed (step N),
(Y), the connection is released and the communication channel is disconnected (process 110), and the communication is terminated.

On the other hand, when the cause of the disconnection of the communication channel is not the network congestion in the processing 105 (processing 105
N), or when the data transfer is completed in the packet switching mode (Y in process 104), the communication is completed in the above procedure (to process 109).

As described above, in this embodiment, there are provided a means for transmitting data in the packet switching mode and a means for transmitting data in the frame mode. At the time of communication, data transfer is first started in the packet switching mode. , During data transfer,
When a communication channel is disconnected due to network congestion, data is transferred in a frame mode.

Since the transmission route in the network differs between the bearer service in the packet switching mode of the IDSN and the bearer service in the frame mode, even if the network is congested and one of the transmission routes is disturbed, the other transmission route is not used. The route is likely to be usable without problems. Thereby, it is possible to minimize the possibility of communication failure during network congestion.

FIG. 5 shows a second embodiment of the communication operation of the data terminal device shown in FIG. That is, in the present embodiment, first, an outgoing / incoming operation is executed in the frame mode bearer service. As a result, a connection for data transfer with the communication partner is set (process 201). Then, data transfer is started (process 202).

In the frame mode, FECN (Forward Explicit) is included in one layer 2 frame.
Congestion Notification)
And BECN (Backward Explicit)
Information (Condition Notification) is allocated. The FECN notifies the frame receiving side of network congestion. BECN is
It notifies the frame transmission side of network congestion. FE
Both CN and BECN are 1-bit data, and are set to “1” when the network is congested.

In this embodiment, when data transfer is started,
The data terminal device on the receiving side uses the FECN in the received frame.
, And the data terminal device on the transmission side checks BECN (process 203). If the data is "0" (N in process 203), the data check is continued while monitoring the remaining amount of transfer data (N in process 204 and process 204) (to process 203). ).

Then, FECN or BECN is "1".
(Y in step 203), the transmission / reception operation is performed by the bearer service in the packet switching mode while maintaining the current data transfer connection. As a result, a connection for data transfer in the packet switching mode is further set for the same destination (step 20).
5).

Thereafter, the data transfer amount in the data transfer connection in the frame mode is reduced, and the data transfer connection in the packet switching mode that has just been set is used.
Try to transfer most of the data. For example, on the frame mode side, 20% of the remaining data is transferred and the remaining 80% is transferred.
% Is transferred on the packet switching mode side (process 206).

In this way, the end of the data transfer is monitored (N loop of process 207). When the data transfer is completed (Y of process 207), the two data transfer connections are released (process 208). To), end the communication.

As described above, in the present embodiment, while the data transfer is started in the frame mode first, when the network is congested, a data transfer connection in the packet switching mode is further set and the two connections are simultaneously established. I am trying to transfer data.

In the packet switching mode, packets that are transmission data are managed in the network, so that packet loss does not occur, but throughput in data transmission is low. On the other hand, in the frame mode, since the network only supports transmission of a layer 2 data frame, transmission data may be lost in the network when the network is congested, but the throughput in data transmission is high. .

In this embodiment, since the data transfer is started in the frame mode first, the data transfer can be performed in a short time by effectively utilizing the high throughput.

When the network is congested during the data transfer, the data transfer amount in the frame mode is reduced,
Most data is transferred in the packet switching mode. As a result, even if the network is congested, the remaining data can be transferred without communication failure.

In the above embodiment, a part of the data is transferred in the frame mode even after the network is congested during the communication in the frame mode. However, after the network is congested, the data is transferred in the packet switching mode. All data may be transferred. As a result, data loss can be completely prevented.

FIG. 6 shows a third embodiment of the communication operation of the data terminal device shown in FIG. That is, in this embodiment, first, two data transfer connections are set in two bearer services of the packet switching mode and the frame mode (process 301). Then, data transfer is started on the connection in the packet switching mode (process 302).

Thereafter, as in the embodiment of FIG. 2, while monitoring the reception of the CI packet or the SI packet (processing 3
03, N in process 303), and monitors the end of the transfer data (from process 304, N in process 304 to process 303).

When a CI packet or an SI packet is received (Y in step 303), it is determined whether the cause of disconnection of the communication channel is network congestion (step 305). Then, in the case of network congestion (Y in step 305), the data transfer in the packet switching mode is stopped, and the data transfer is immediately switched to the data transfer in the frame mode (step 30).
6). Thereafter, the end of the transfer data is monitored (step 30).
7 (N loop in process 307), when the process is completed (Y in process 307), 2
The two data transfer connections are simultaneously released (process 308), and the communication is terminated.

In the embodiment shown in FIG. 2 or FIG. 5, after a trouble occurs in the data transmission in one data transfer connection, a certain outgoing / incoming call procedure is executed to set the other connection. Therefore, in some cases, the other connection cannot be set. In that case, data transfer had to be stopped.

In this embodiment, as described above, 2
Since the types of data transfer connections are set in advance, when data transfer becomes impossible in one connection, data transfer can be surely continued in the other connection.

In the above embodiment, when two types of data transfer connections are set, a method using both ISDN B (information) channels and a method using two types of data transfer connections using only one channel are used. There is a way to set. In this case, if a method using only one channel is adopted, it is possible to prevent the data terminal device of the present embodiment from occupying the B channel when another terminal device is connected to the same line. Can be.

In the above embodiment, first, the data transfer is started on the connection in the packet switching mode. However, the data transfer may be started on the connection in the frame mode. is there.

Further, in each of the above embodiments, it is assumed that the communication failure and the loss of the transmission data occur when the network is congested. However, for example, it may also occur due to an accident or a failure in the network. Therefore, even in the event of an accident or a failure in the network, the same operation and effect can be obtained by performing the same operation.

Next, a description will be given of a fourth embodiment of the communication operation of the data terminal device shown in FIG.

In this embodiment, it is assumed that image data is transmitted by this data terminal device. When executing the transmission process, the transmission-side operator inputs image information to be transmitted from the input unit 1 and stores the image information in the storage unit 3. In this case, the image information to be stored may be raw image information obtained by reading a document image with a scanner device, or image information obtained by compressing the image information by a known encoding method.

After accumulating the image information, the operator specifies to the data terminal device the type of the image information indicating whether the stored image information is raw image information or image data obtained by data compression. In addition, a communication mode called a packet switching mode or a frame mode is designated as necessary. After these operations, the communication partner is set and the device is started.

When the data terminal device is activated, it determines whether or not the communication mode is specified, as shown in FIG. 7 (process 401).
Here, when the packet switching mode is designated (Y in process 401), a data transfer connection with a communication partner is set in the outgoing / incoming call procedure in the packet switching mode, and image information is transmitted (process 402). .

On the other hand, if the packet switching mode is not specified (N in step 401), it is determined whether or not the frame mode is specified (step 403). If the frame mode has been designated (Y in step 403), a connection for data transfer is set with the communication partner in the transmission / reception procedure in the frame mode, and image information is transmitted (step 404).

If the communication mode is not specified (N in step 403), the type of image information is determined (step 405). If the image information is compressed (Y in step 405), the image information is transmitted by the data transfer connection in the packet exchange mode (step 402).
What). On the other hand, if the image information is raw image information (N in step 405), the image information is transmitted through the frame mode data transfer connection (to step 404).

When the transmission of each piece of image information ends, the connection is released (step 406), and the transmission processing ends.

By the way, in the packet switching mode, transmission data is not lost in any case, so that image information can be transmitted reliably. On the other hand, since the data transmission throughput is low, communication time is required.

On the other hand, in the frame mode, since the data transmission throughput is high, communication can be performed in a short time. On the other hand, transmission data may be lost when the network is congested.

In this embodiment, since the communication mode can be arbitrarily selected by the operator, when transmitting image information, priority is given to accuracy of image information or priority to communication in a short time. In response to the operator's request.

When the operator does not specify the communication mode, the image information that has been compressed is transmitted in the packet switching mode, and the raw image information is transmitted in the frame mode.

If even one bit is missing from the compressed image information, the original complete image information cannot be restored. However, since the data is accurately transmitted in the packet switching mode, the original complete image information is restored on the receiving side. I can do it.

On the other hand, since the raw image information is transmitted in the frame mode, it can be transmitted in a short time. In this case, when the network is congested, there is a possibility that a transmission frame is lost in the network. However, if the raw image information has few missing data, only a part of the image will be lost, and there is no problem in practical use.

In the above embodiment, when image information is transmitted, the packet switching mode and the frame mode are selectively used depending on the type of the image information. Similarly, the same operation and effect can be obtained by selectively using the two communication modes.

[0058]

As described above, according to the present invention, the ISD
Since two transmission means of the N packet switching mode and the frame mode are provided, and data transmission is started in the frame mode first, data transmission can be performed in a short time by effectively utilizing high throughput. If the network becomes congested during the data transmission, a packet switching mode is added to perform data transmission over two connections at the same time, reduce the amount of data transmission in the frame mode, and increase the amount of data transmission in the packet switching mode. Part of the data is transmitted. As a result, even if the network is congested, the remaining data can be transmitted without being incapable of communication, and communication trouble due to network congestion can be minimized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a data terminal device according to one embodiment of the present invention.

FIG. 2 is an operation flowchart showing a communication operation of the data terminal device according to a first embodiment;

FIG. 3 is an explanatory diagram of a communication state in a packet switching mode.

FIG. 4 is an explanatory diagram of a communication state in a frame mode.

FIG. 5 is an operation flowchart showing a second embodiment of the communication operation of the data terminal device.

FIG. 6 is an operation flowchart showing a third embodiment of the communication operation of the data terminal device.

FIG. 7 is an operation flowchart showing a fourth embodiment of the communication operation of the data terminal device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input part 2 Output part 3 Storage part 4 ISDN communication part 5 Operation display part 6 System control part

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-235555 (JP, A) JP-A-62-180639 (JP, A) JP-A-3-175855 (JP, A) Supervised by Minoru Akiyama “ISDN The Picture Book, 1st Edition, published December 10, 1989, Ohmsha, p. 152 (Evolution of packet communication and OSI) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04L 29/14

Claims (1)

(57) [Claims] 1. An ISDN data terminal device comprising two data transmission means of a packet switching mode and a frame mode, wherein at the start of communication, means for starting data transmission with a communication partner in the frame mode, Means for detecting congestion; means for, when network congestion is detected, maintaining data connection in the frame mode, and starting data transmission in the packet switching mode; and data transmission in the frame mode. Means for increasing the amount of data transmission in the packet switching mode than the amount of data.