JPH03139043A - Cell missing and mis-transfer detection system in atm exchange - Google Patents

Abstract

PURPOSE:To detect missing cell and mis-transfer by adding an information source identifier indicating an information source and a sequence number of consecutive information in addition to a header of each cell to the cell and sending the resulting cell. CONSTITUTION:Consecutive information generated from a consecutive information source is divided into cell by split means 11 of a transmission section 10 and a sequence number for each cell is added to each cell by a sequence number addition means 12 and indication of an information source is added by an information source identification provision means 13. Moreover, a header provision means 14 adds header information to a head of the cells and the result is outputted to an ATM exchange system 15. A header is eliminated by a header elimination means 17 from a cell inputted to a destination reception section 16 from the system 15 and the information source identifier in the cell is discriminated by a succeeding mis-transfer detection means 18. Then a cell missing detection means 19 checks the sequence address in the received cell. Moreover, a consecutive information decoding means 20 decodes the cell outputted from the means 19 into the consecutive information and outputs the result.

Description

[Detailed Description of the Invention] [Summary] Regarding a cell dropout and erroneous delivery detection method in ATM exchange, the present invention provides a cell dropout and erroneous delivery detection method in ATM exchange that can easily detect and deal with cell dropout and erroneous delivery. For the purpose of A sequence number addition means for adding a sequence number, an information source identifier addition means for adding an information source identifier to each information source of the continuous information, and a header addition means are provided, and a header is added to a receiving unit that inputs information from an ATM switching system. A deletion means, an erroneous delivery detection means for detecting erroneous delivery using an information source identifier, a cell omission detection means for detecting cell omission using a sequence number, and a means for restoring received cells to continuous information are provided. Configure.

[Industrial Field of Application] The present invention relates to a method for detecting missing cells and erroneous delivery in ATM exchange, and in particular, the present invention relates to a method for detecting missing cells and erroneous delivery in ATM exchanges, and in particular uses CBO (Continuous Confidence) as an information source where the form of generation of information is continuous in time, such as voice or moving images.
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This invention relates to a detection method when a cell carrying this CBO information is discarded or erroneously transmitted to a different receiving side in the switching system when performing ATM switching for ed).

ATM (Async) is attracting attention as a next-generation network.
In the case of the transmission method (Hronous Transfer Mode), information is transmitted, for example, in blocks of several tens of bytes (hereinafter referred to as cells). A header containing the address of the receiving side is added to this cell, and the switching system uses this header to transmit the cell to the receiving side. Compared to conventional circuit switching methods, this method does not guarantee that cells will be reliably transmitted to the receiving side;
Cells may be discarded within the network due to traffic congestion within the network, or cells may be erroneously transmitted to a different receiving side due to a bit error in the header. For this reason, cells may not reach the receiving side due to discarding, erroneous delivery, etc., and it is desired to detect and deal with such situations.

[Conventional technology 1 As a conventional switching method, circuit switching method (STM: 5
synchronous Transfer Mode)
In this case, there are ways to detect and deal with bit-wise errors.

That is, errors in transmitted information are detected using check bits and the like.

In addition, in the case of conventional packet switching methods, it is used to transmit burst information such as data, and information is transmitted without establishing a connection path with the other party (this is called connectionless transmission). ), the transmission path for each packet is not fixed on the transmission path. Therefore, it was necessary to use sequence numbers in order to reproduce the packet transmission order on the transmitting side on the receiving side. However, in a connection-oriented system such as ATM, in which a call setup phase is executed at the beginning of communication to establish a connection with the other party, and then information is transmitted, such sequence numbers are not considered.

[Problem to be solved by the invention] When performing CBO services that transmit audio, video, etc. through ATM exchange, in the conventional system, if a cell is dropped or a misdelivery occurs, temporal continuity is no longer maintained and audio cannot be transmitted. There have been problems with images being interrupted, noise, or unnatural images occurring.

SUMMARY OF THE INVENTION An object of the present invention is to provide a cell dropout and erroneous delivery detection method in ATM switching that can easily detect and deal with cell dropout and erroneous delivery.

[Means to solve the problem 1 FIG. 1 is a diagram showing the basic configuration of the present invention.

In FIG. 1, 1 is a transmitted cell configuration, 10 is a transmitter, 11 is a dividing means for dividing continuous information into cells, 12 is a sequence number adding means, 13 is an information source identifier adding means, and 14 is a header adding means. means.

Reference numeral 15 represents an ATM switching system, 16 a receiving unit, 17 a solder deletion means, 18 an erroneous delivery detection means, 19 a cell removal detection means, and 20 a continuous information restoration means.

In order to transmit time-continuous information by ATM exchange, the present invention adds an information 'a identifier indicating the information source and a sequence number of continuity information in addition to the header of each cell, and transmits and receives the information. By detecting this information on the side, missing cells and erroneous deliveries can be detected and dealt with.

In Figure 1, continuous information generated from a continuous information source is
The dividing means 11 of the transmitter 10 divides each cell into cells, and the next sequence number adding means 12 adds a sequence number for each divided cell, and then displays the information source from which the information is generated. rA identifier addition means 1
Add with 3. Furthermore, header information is added to the beginning of the cell containing these additional information by the header adding means 14 in the same manner as in the past.

The format of the cell with header information added and output to the ATM switching system is shown in the figure as cell configuration 1. In this way, a cell is composed of a header, an information a identifier, a sequence number, and information of a predetermined length.

The header of the cell input from the ATM switching system 15 to the receiver 16 of the other party is deleted by the header deletion means 17, and the information tA identifier in the cell is determined by the next erroneous delivery detection means 18. The information source identifier is extracted from the first received cell and held, and it is determined whether the information of cells received thereafter is the same or not. If they are not the same, the cell is discarded as an erroneous delivery. Alternatively, at the time of call setup, the value of this information source identifier is notified to the receiving section 16, and the cell is discarded by the same means as described above.

Next, the cell omission detecting means 19 checks the sequence number in the received cells, checks whether or not the cells are received in order, and if it detects that the number is skipped, the cell omission Assuming that a problem has occurred, processing such as inserting alternative information is performed. Finally, the continuous information restoring means 20 restores the cells outputted from the cell omission detection means into continuous information and outputs it to an audio or image terminal device.

[Embodiment] FIG. 2 is a diagram showing a configuration of an embodiment of the present invention, and FIG. 3 is a diagram showing a self-automated system of the embodiment.

In Fig. 2, 2 is a transmitter, 3 is a receiver, 4 is A, T
M represents an exchange system. Further, as shown in FIG. 3, the cell of the embodiment has 5 bytes of header information.

4-bit sequence number, 4-bit source identifier,
It is composed of 47 bytes of divided audio information, and has a total length of 53 bytes.

To explain the operation, in this embodiment, audio is used as the CBO information source as described above. In the case of audio.

It becomes a continuous information source of 64Kbps. Continuous information input from the audio terminal is divided into four
Each cell (information portion) is constructed by dividing into 7-byte blocks. This cell is then inserted into the insertion circuit 22
At (indicated by the symbol e in the figure, the same applies hereinafter), a 4-bit sequence number supplied from the sequence number adding section 23 is added. The sequence number is sequentially increased (incremented) for each cell, and all 4 pins are “1” (1
(corresponding to 15 in base 0), then we start counting from 0.

The cell to which the sequence number has been added is sent to the next insertion circuit 24 for information il! The 4-bit information a identifier supplied from the X identifier adding section 25 is inserted.

In the information source identifier adding section 25, an information source identifier is set in advance in an internal register (not shown).

For example, if the transmission band is wide (about 150 Mbps), such as in a system intended for multimedia transmission,
Although voice communication may be performed simultaneously from multiple terminals on the transmitting side, a different information source identifier is set for each terminal.

Next, the header information deletion unit 26 deletes the 5-byte header (
) is added, and the other party's address is included in it. This cell is transmitted to the ATM switching system 4, where an exchange operation is performed using the header, and the cell is transferred to the receiving unit 3 on the other side.

When the receiving unit 3 receives a cell, the header is deleted in the header information deletion unit 31, and the primary extraction circuit 32 (indicated by the symbol e in the figure) deletes the information source identifier (
4 bits). The extracted information source identifier is used in the erroneous delivery detection unit 33 to identify whether the cell is erroneously delivered due to a bit error in the header. This identification is compared with the configured information source identifier. The set information source identifier is set by extracting the information source identifier included in the cell first sent from the transmitting side.

Therefore, if the detection operation is performed on the information source identifiers of the second and subsequent cells, and the information tX identifier of the received cell and the set information source identifier do not match, it is determined that the cell has been delivered in error. A control n output representing the output is generated from the erroneous delivery detection unit 33 and switches the switch 34. The cells received by this switching are discarded.

Note that another possible means for the receiving side to know this information source identifier is to notify the receiving side at the time of call setting in the same way as other call setting parameters.

If there is no error in the information a identifier, the switch 34 remains in its position and the cell (from which the source identifier has been removed) is sent to the next stage circuit.

The extraction circuit 35 extracts the sequence number. The extracted sequence number is compared with the sequence number held therein in the cell extraction detection section 36 to check continuity.

In other words, when this cell is removed, the detection unit 36 holds a value obtained by adding 1 to the sequence number received last time, and if the cell information received this time matches this held sequence number, it follows the cell received last time. It is detected that a cell has been received, and if they do not match, it is assumed that a cell dropout has occurred, and a control output for switching the switch 37 is generated.

When the switch is changed over, dummy information is output from the dummy information creation unit 38 as information in place of the cell in which the cell dropout has occurred. This dummy information creation unit generates certain data (for example, the data of the cell that was received just before,
Noise data that is not harsh to the human ear (such as all “1” or all “0”) is output, and the next F
I F O (First In First 0ut)
It is input to the buffer 39.

The FIFO 39 stores the sequentially input cells (parts of the divided audio information in FIG. 3) starting from the top position and restores them to the original continuous information. The restored continuous information is read out in the order written to the terminal device (not shown),
The audio information is reproduced through processing such as DA conversion.

[Effects of the Invention] According to the present invention, in a cell-by-cell information transmission system such as an ATM switching system, it is possible to detect cell discard and erroneous delivery when continuous information such as voice is used as an information source, and to reduce the effects at the time of detection. It becomes possible to reduce the amount.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic configuration of the present invention, FIG. 2 is a diagram showing the configuration of an embodiment, and FIG. 3 is a diagram showing a self-automated system of the embodiment. In Figure 1. 1: Cell configuration 10: Transmitting section 12 consecutive information dividing means 12 sequence number adding means 13: Information source identifier adding means 14: Header adding means 15: ATM exchange system 16: Receiving section 17: Header deleting means 18: Error Delivery detection means 19: Cell removal is detection means 2022 consecutive information recovery means

Claims (1)

[Claims] In a cell dropout and erroneous delivery detection method in an ATM exchange, a transmission unit (10) that outputs information to the ATM exchange system is provided with a continuous transmission unit that divides information from an information source that occurs continuously in time. information dividing means (11); sequence number adding means (12) for adding consecutive sequence numbers to each divided cell; and information source identifier adding means (12) for adding an information source identifier to each information source of the continuous information. 13) and a header adding means (14), and a receiving section (16) that inputs information from the ATM exchange system (15) is provided with a header deleting means (17) and an information source identifier to detect erroneous delivery. erroneous delivery detection means (18);
An ATM exchange characterized in that it is provided with a cell dropout detection means (19) that detects cell dropout using a sequence number, and a continuous information restoration unit (20) that restores divided information to the original continuous information. Missing cell and erroneous delivery detection method.