JPH03187642A - I interface subscriber line test method - Google Patents

Abstract

PURPOSE:To attain a dynamic loopback test by sending a test frame signal in the case of the loopback test via an LAP-D means, inverting CR bits and returning the result to the LAP-D means. CONSTITUTION:A host controller 7 sends a test data to a subscriber circuit 3 via an LAP-D device 6. The C/R bit of the data is set to a command '1', the data is sent from a transmission line S to a subscriber termination circuit 30, where the signal is looped back and transferred from a reception line R to a bit inversion circuit 32. The bit inversion circuit 32 outputs the logic of the C/R bit with inversion and the LAP-D device 5 receives the data whose C/R is converted into '0' and it is informed to the host controller 7. The host controller 7 compares it with a sent data to discriminate the normality. Thus, the dynamic line loopback test is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for testing subscriber lines, particularly for
The present invention relates to an interface subscriber line testing method that is advantageously applied to digital exchanges such as exchanges.

(Prior art) For example, CCI applied to the l5DN exchange system
The TT Recommendation I series and I Recommendation series I interface include:
0SI(Open 5ystetsss Interco
The configurations of layer 1 (physical layer), layer 2 (data link layer), and layer 3 (network layer) of the layer model of nnection) are defined. layer 2
The data link layer transmits data in frames,
Each frame is defined as whether it is a command frame (command) or a response frame (response). The protocol is then executed by receiving a response to the command transmission.

The command/response distinction is indicated by the C/R bit in the address part of the frame. Specifically, when a terminal accommodated in an 15DN exchange sends a command to the network side, C/R
C when the bit is set to 0 and a response is sent.
/R bit is set to "1". Also, the network (exchange)
In the case of , the logic of the C/R bit is reversed, and the C/R bit is "1" when sending a command from the network to the terminal side.
is set, and when sending a response, the C/R bit is set to “
0”. CCITY Recommendation 1.430 determines the setting of the C/R bit on the network side and the terminal side in this way.

There are three formats of control fields in frames: F format, S format, and U format, and F format is used for testing between terminals and the network.

Therefore, in this case, there is no response, only a command.

For example, if data is frequently corrupted or lost when data is exchanged between the subscriber terminal and the higher-level control device of the exchange, it is likely that the cause is a disconnection between the exchange and the terminal. The exam will be held in minutes. In other words, for example, if the exchange tries to perform a test on the route to the subscriber terminal, the exchange sets the loop back to the subscriber circuit that accommodates the subscriber terminal, and reads the loop setting state. It was possible to determine whether the fault was on the terminal side or on the exchange side.

(Problem to be Solved by the Invention) However, in such conventional technology, since the logic of the C/R bit is determined by CCITT Recommendation 1.430, fault isolation requires loopback at the frame level during testing. It was impossible to implement. This is C/
Since the logic of the R bit is opposite between the user side and the network side, for example, if the exchange side sends test data to the terminal side and returns it as is, the C/R bit will be checked midway and the frame will be discarded as an invalid frame. This is because it will be done. Therefore, in the prior art, when performing such a test, the test is performed by attaching an external monitor device or attaching a pseudo terminal. For this reason, failures could only be detected in a static state, making dynamic testing impossible.

SUMMARY OF THE INVENTION An object of the present invention is to provide an I-interface subscriber line testing method that eliminates the drawbacks of the prior art and allows dynamic loopback testing.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides: (1) subscriber means for accommodating an interface subscriber line and terminating the first layer on the interface; An interface subscriber line testing method applied to a switching device having a terminating LAP-0 means is to send a test frame signal through the LAP-0 means during a loopback test, and check the CR of the sent test frame signal. The bits are inverted and sent back to the LAP-0 means.

(Function) According to the present invention, during a loopback test, a test frame signal is sent out via the LAP-0 means, and the CR bit is inverted and sent to the LAP-0 means.

(Embodiment) Next, an embodiment of the interface subscriber line testing method according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a relay system diagram when the I-interface subscriber line testing method according to the present invention is applied to an I5DN exchange. The I5DN exchange I19 has a plurality of subscriber circuits 3, a LAP-D device 5, and a higher-level control device 7, and connects a plurality of data terminal devices (TE
) is a digital exchange that accommodates Note that in the figure, components of the exchange 9 that are not directly related to the present invention are omitted.

The subscriber circuit 3 is a subscriber circuit that accommodates a data terminal device l having an I interface via a subscriber line 100 and terminates a physical layer, which is layer l. The terminal interface between the subscriber circuit 3 and the terminal device 1 consists of two independent E! It consists of a 4 Kb/s information channel (B channel) and one 18 Kb/s signal channel (D channel), and is indicated by 2B10.

The subscriber circuit 3 includes a subscriber line termination circuit 30, a bit reversal circuit (RV) 32, a LAP-D interface circuit 34, and a test mode reception control circuit (TG'03Ei).

The subscriber line termination circuit 30 is a subscriber circuit that is connected to the terminal device 1 via the subscriber line 100 and provides an I interface therewith. That is, the subscriber line termination circuit 30 connects the transmission line interface of the subscriber line 100 to the transmission line S in the circuit.
It also has the function of converting into the logic level of the receiving line H.

Further, the subscriber line terminating device 30 includes a return control line 130
It is connected to the test mode reception control circuit 36 via.

When the subscriber line termination device 30 receives a return instruction from the test mode reception control circuit 3B via this control line 130,
A subscriber line termination device 30 that performs loopback settings for the transmission line S and the reception line H connects the interface circuit 3 via the transmission line S.
4 is connected to a bit inverting circuit 32 via a receiving line R.

The bit inversion circuit 32 converts a frame 300 (second
It has the function of inverting the C/R bit included in address A in the figure. That is, the bit inversion circuit 32 is connected to the test mode reception control circuit 3 via the C/R bit inversion control line 132.
6 and outputs the C/R bit as it is during normal data transfer, and when there is an instruction to invert the test mode from the reception control circuit 3B, the C/R bit of the received frame is output as is.
The state of the R bit is inverted and output. Bit inversion circuit 3
2 is also connected to the LAP interface circuit 34 via the receiving line R.

The test mode reception control circuit 36 is a control device that controls the subscriber line termination circuit 30 and the bit inverting circuit 32 during a return test on the network side, that is, on the exchange 9 side in this embodiment. The test mode reception control circuit 36 connects the signal line 200
When receiving a return instruction from the host controller 7, it controls the subscriber line termination circuit 30 and the bit inversion circuit 32 to a test mode.

The LAP-D interface circuit 34 connects the transmission line S and the reception! ! This is an interface circuit that is connected to the LAP-D device 5 via jR and performs data transmission and reception with this device.

The LAP-D device 5 is a device that manages the data link layer, which is layer 2. Specifically, it performs the link access protocol on the D channel, that is, the order of information transfer, error control, etc., and terminates layer 2. For example, if the logic of the C/R bit of a frame received from the subscriber circuit 3 does not match, the LAP-D device 5 discards the frame as an invalid frame. Each LAP-D device 5 is connected to the host control device 7 via a signal 1i200.

The upper control device 7 is a level conversion device that converts layer 2 to layer 3 level. The higher-level control device 7 also sets the subscriber circuit 3 in a test mode when performing a return test on the subscriber circuit 3, and also sends test data to the LAP-D device 5 and instructs its transfer. 7
In response to a loopback test instruction from , the test mode reception control circuit 36 sets the subscriber line termination circuit 30 and the bit inversion circuit 32 to the test mode via control lines 130 and 132.

Thereby, the subscriber line terminating device 30 connects the transmission line S and the reception line R in a loop. The bit inversion circuit 32 also controls the C/R of the transmission frame received from the reception line R.
Inverts the logic of a bit.

FIG. 2 shows the format of a data frame 300 transmitted to the subscriber line 100 and signal lines S and H, that is, CCIT.
The frame format at TQ, 921 is shown.

Frame 300 has address A, flJ control field C
1 information I and each bit of frame check sequence FCS. As shown in the figure, the C/R bit indicating the command/response is included in the address field A along with an extension bit (EA), a service access point identifier (SAPI), a termination point identifier (TEI), etc.

Note that the control field C has three formats: the ■ format, the S format, and the U format, but the I format is used in the one-line test. Therefore, in the case of a line test, there are only commands and no responses.

FIG. 3 shows the logical states of the C/R bits in commands and responses on the network side and terminal side. In this way, the logic on the terminal side and the network side is reversed, so C/R
Line test data with bit “1” is looped back and sent to LAP.
When received by the -D device 5, it is discarded by this device 5 unless it is inverted and the C/R bit becomes "0".

■Explain the return test for interface subscriber lines. First, the host controller 7 sends C to the subscriber circuit 3.
/R bit inversion instruction is issued, thereby subscriber circuit 3
The test mode reception control circuit 36 in the C/R bit inversion circuit 32 transmits a bit inversion instruction to the C/R bit inversion circuit 32. Next, the host control device 7 gives a return instruction to the test mode reception control circuit 36 of the subscriber circuit 3. As a result, when the test mode reception control circuit 3B performs return control on the subscriber line termination circuit 30, the subscriber line termination circuit 30 connects the transmission line S and the reception line R in a loopback manner.

After giving these instructions to the subscriber circuit 3, the upper control device 7
sends the test data to the LAP-D device 5 and instructs it to be transferred. Upon receiving this instruction, the LAP-D device 5 sends out the data in the above-mentioned I format frame. The C/R bit of the data at this time is set to "1" in the command. This data is transmitted from the transmission line S to the LAP-D interface circuit 3 in the same way as normal transmission.
4 to the subscriber line termination circuit 30. The signal is then turned back at the termination circuit 30 and transferred from the reception line R to the bit inversion circuit 32.

Since the bit inversion circuit 32 has received a bit inversion instruction at this time, it inverts and outputs the logic of the C/R bit included in address A. As a result, the test data with the C/R bit inverted passes through the interface circuit 34 and is sent to the LAP-D.
It is sent back to device 5. The LAP-D device 5 receives data in which the C/R bit has been converted to rOJ as a command, and notifies the upper control device 7 of this. The upper control device 7 reads the received data and compares it with the transmitted data to determine normality.

In this way, according to this embodiment, ■ the switching device 9 having an interface subscriber line is provided with a function that can invert the C/R bit for the LAP-D device 5, and , the logic of the C/R bit of the command/response can be inverted. This makes it possible to perform loopback tests at the frame level, and even if data is frequently garbled or lost between the terminal device 1 and the higher-level control device 7, it is possible to determine whether the cause is the terminal, the line, or the like. It is possible to dynamically distinguish between exchanges.

Note that the embodiments described here are for explaining the present invention, and the present invention is not necessarily limited thereto, and modifications and variations that can be made by those skilled in the art without departing from the spirit of the present invention. Modifications are within the scope of this invention. That is, in this embodiment, the C/R bit inverting function is provided on the receiving line R side of the subscriber circuit 3, but of course the inverting function may also be provided on the transmitting line S side. A C/R bit inversion function may be provided in the subscriber terminal device l.Furthermore, if a return connection function is provided in the subscriber terminal device l, a line test including the subscriber line 100, which is a transmission path, can be performed. Therefore, if this is used in combination with this embodiment, it becomes possible to perform a test to isolate faults between the inside of the exchange and the outside including transmission lines, terminals, etc.

(Effects of the Invention) As described above, according to the present invention, by providing the C/R bit inversion function, it is possible to perform a dynamic line loopback test while complying with the current CCITT recommendations. Therefore, it is possible to improve both switch maintenance and line maintenance in a digital network such as an 15DN network.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a relay system diagram showing an embodiment in which the A-interface subscriber line testing method according to the present invention is applied to an I5DN switch; FIG. 3 is an explanatory diagram showing the logical state of the C/R bit on the terminal side and the network side. 1. 3. 5. 7. 30゜32゜34゜36, Explanation of symbols of main parts, data terminal equipment, subscriber circuit, LAP-D equipment, host control equipment, subscriber line termination circuit, C/R bit inversion circuit, LAP-D interface circuit , test mode reception control circuit 00 Frame format used in this embodiment Fig. 2 Logic state of C/R bit Fig. 3

Claims (1)

[Scope of Claims] Applicable to switching equipment having subscriber means accommodating a 1,1 interface subscriber line and terminating a first layer on the interface and LAP-D means terminating a second layer. The I-interface subscriber line testing method is as follows: during a return test, a test frame signal is sent through the LAP-D means, the CR bit of the sent test frame signal is inverted, and the CR bit is sent to the LAP-D means. A method for testing an I-interface subscriber line, which is characterized by returning the signal. 2. The subscriber line testing method according to claim 1, wherein the method includes the function of inverting the C/R bit by the subscriber means,
between said subscriber means and said LAP-D means and said LA
1. A method for testing an I-interface subscriber line, characterized in that it is provided in any of the PD means. 3. The subscriber line testing method according to claim 1, wherein the test frame signal is looped back by an external device connected to the subscriber line, the subscriber means, and the LAP.
- An I-interface subscriber line testing method characterized in that it is carried out by any one of the D means.