JPH09233091A - Communication equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the transmission failure in the case of re-transmission by dividing transmission data into two and sending again the data to a newly sat virtual path or a virtual channel and also to a virtual path or a virtual channel designated precedingly when transmission of the transmission data is failed. SOLUTION: A communication terminal equipment 11 at a transmitter side divides transmission data into cells and sends them to a master equipment 12. When a communication terminal equipment 11 at a receiver side detects a missing cell in the received data, the terminal equipment 11 sends information denoting failed transmission to the communication terminal equipment 11 at the transmitter side. Upon the receipt of the information, the terminal equipment 11 at the transmitter side sets newly a different virtual path(VP) or a virtual channel(VC) from the VP or the VC set for the preceding transmission and divides the transmission data and sends the resulting data to plural VPs or VCs including the newly set VP or VC. When the transmission is not yet successful, a VP or a VC is newly set again and the transmission data are divided again and the resulting data are set again.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in communication success rate at the time of retransmission of a data communication terminal which performs data communication using an asynchronous transfer mode.

[0002]

2. Description of the Related Art In an asynchronous transfer mode, all information is carried in fixed length blocks called cells, regardless of communication media such as voice, video and data.

A cell is composed of a header part and an information field part, and an identifier indicating a destination is stored in the header part. The cell is transferred to the destination using the identifier in this header part. In this way, in a communication network that uses the asynchronous transfer mode, all information is stored in cells of the same shape and processing such as multiplexing, demultiplexing, and switching is performed, so the same network can be used without being aware of the differences in communication media. Information can be transferred centrally.

In a communication device for transmitting and receiving cells using such an asynchronous transfer mode, when it is necessary to transmit a large amount of data in bursts at once, the main device connected to the line is overloaded. Or the line is overloaded, cell loss occurs and the transmitted data is normally discarded. In this state, the receiving terminal sends the transmission failure information to the transmitting side, and the transmitting side takes measures such as retransmission.

By the way, a virtual path identifier (hereinafter referred to as VPI) and a virtual channel identifier (hereinafter V
The identifier (denoted by CI) is stored, and the connection to which the cell belongs is identified by the combination of these values. The values of VPI and VCI are determined when the connection is established and are held until the connection is released.

However, conventionally, when retransmitting in response to occurrence of cell loss, the same virtual path (hereinafter referred to as VP) or virtual channel (hereinafter referred to as VC) is used (same VPI and VCI are set). However, there is a problem in that it often fails to communicate because of failure in resending.

Now, terminal 1, terminal 2 and terminal 3 are each 100
Consider the case of transmitting cells one by one. In the worst case, due to the line overload condition, cell loss for each line (10 at each terminal)
Cell by cell), all transmission data is discarded, and communication with three terminals is impossible. After that, even if the same VP and VC are used even if retransmission is performed, the same state may be repeated, and similarly, there is a possibility of returning to a state in which communication with three terminals is not possible.

[0008]

As described above, in the conventional communication terminal, when communication fails, the same VP and VC are used again to perform retransmission, so that there may be cases where communication fails due to repeated failures. There were many problems.

An object of the present invention is to eliminate this problem and to realize a communication terminal capable of reducing transmission failure at the time of retransmission.

[0010]

In order to achieve the above object, the present invention is a communication device for transmitting and receiving transmission data composed of a plurality of cells by using an asynchronous transfer mode. When the transmission of the transmission data fails due to the above, a virtual path or virtual channel different from the virtual path or virtual channel specified last time is newly set, and the newly set virtual path or virtual channel and the previous time It is characterized in that the transmission data is divided into the virtual path or virtual channel specified in 1 above and retransmitted.

When the transmission of the transmission data fails again when the transmission data is retransmitted, a virtual path or virtual channel different from the virtual path or virtual channel designated last time is newly set, and the transmission data of the transmission data is transmitted. It is characterized in that the number of divisions is increased and retransmission is further performed.

According to the present invention, when retransmitting, a new VP and VC are used, and the data is divided and retransmitted. As a result, the same state is less likely to be repeated, and transmission failures at the time of retransmission can be reduced.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A communication device according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a network configuration diagram of a communication device according to an embodiment of the present invention. In the figure, 11 is a communication terminal, 12 is a main device connected to a line, and 13 is a line. Further, FIG. 2 is a connection diagram when the transmission data between the communication terminal 11 and the main device is not divided, and there is one VP. FIG. 3 is a connection diagram when the transmission data between the communication terminal 11 and the main device 12 is divided, and shows a case where the number of VPs is two.

The operation of this communication terminal will be described below.

The communication terminal 11 on the transmitting side divides the transmission data into cells and transmits the cells to the main unit 12.

When the communication terminal 11 on the receiving side detects a missing cell in the received data, it transmits information indicating that the transmission has failed to the communication terminal 11 on the transmitting side. Upon receiving this transmission failure information, the communication terminal 11 on the transmitting side newly sets a plurality of VPs or VCs different from the VPs or VCs set in the previous transmission, and a plurality of VPs including the newly set VPs or VCs. Alternatively, the transmission data is divided into VCs and transmitted.

As an example, the communication terminal 11 on the transmitting side is 100
Consider the case of transmitting cells.

FIG. 2 shows a connection diagram before division of the VP. It is assumed that the communication terminal 11 on the transmitting side has transmitted 100 cells to the path having the VPI of 1, but the transmission has failed due to cell loss between the communication terminal 11 and the main device 12. Therefore, upon retransmission, the transmission-side terminal 11 sets a path with a VPI of 2 as a new VP as shown in FIG. 3 and sets 100 cells to a path with a VPI of 1 to 50 cells and a path with a VPI of 2 to 50 cells.
It is divided into cells and sent.

As a result, even if the cell omission is caused by the path having the VPI of 1, the number of cells passing through the path having the VPI of 1 is reduced, and the cell omission probability is reduced.

Since the path having the VPI of 2 is newly set, the probability of cell loss is lower than that of the path having the VPI of 1 in many cases.

However, depending on the state, even if the division is performed in this way, it may further fail. In this case, a new V
P is set so that data for which communication has failed is further divided and transmitted. FIG. 4 shows a case where 25 cells are transferred by using four VPs.

FIG. 5 is an operation flowchart of the terminal 11 when performing communication by such a method. After the transmission operation is started (step 100), the transmission is performed (step 1)
01) to see if the transmission was successful (step 1
02), if successful, the transmission operation ends (step 105). If not successful, a new VP (or V
After setting C) (step 103) and dividing the transmission data (step 104), the transmission is performed again (step 101).

If this transmission also fails, a new VP (or VC) is set (step 103),
After further dividing the transmission data (step 10)
4) Then, the process of transmitting again (step 101) is repeated.

In the above embodiment, the VP is divided, but it is needless to say that the same can be realized by dividing the VC. Whether to divide by VP or VC is selected depending on the situation at that time.

Further, in the above explanation, V is set on the communication terminal 11 side.
Although P or VC is divided, the division may be performed on the main device 12 side.

[0027]

As described above, according to the present invention, when transmission fails due to a cell drop or the like, a virtual path or virtual channel different from the virtual path or virtual channel designated last time is newly set, and each virtual path or virtual channel is set. The transmission data is divided into the path or virtual channel and then transmitted.

When the transmission fails again, a plurality of virtual paths or virtual channels different from the virtual path or virtual channel designated last time is newly set, and the transmission data is further divided before transmission. To do so.

As a result, the same state is less likely to be repeated, transmission failures at the time of retransmission can be reduced, and as a result, efficient communication can be realized.

[Brief description of drawings]

FIG. 1 is an example of a network configuration of a communication device according to an embodiment of the present invention.

FIG. 2 is a connection diagram of a communication terminal and a main device before division.

FIG. 3 is a connection diagram of the communication terminal and the main device after the division according to the present invention.

FIG. 4 is a connection diagram of a communication terminal and a main device after further repeating division according to the present invention.

FIG. 5 is an operation flowchart at the time of transmission of the communication terminal that executes the present invention.

[Explanation of symbols]

 11 communication terminal 12 main device 13 line

Claims (2)

[Claims] 1. In a communication device for transmitting and receiving transmission data composed of a plurality of cells by using an asynchronous transfer mode, when transmission of the transmission data fails due to a cell drop or the like when transmitting the transmission data, A new virtual path or virtual channel different from the virtual path or virtual channel specified in, and divides the transmission data into the newly set virtual path or virtual channel and the previously specified virtual path or virtual channel. A communication device, characterized in that the communication is retransmitted. 2. When retransmitting the transmission data, if the transmission of the transmission data fails again, a virtual path or virtual channel different from the virtual path or virtual channel designated last time is newly set, and the transmission data is transmitted. 2. The communication device according to claim 1, wherein the number of divisions is increased and further retransmitted.