FR2631194A1 - Method of remote maintenance and supervision of point-to-point links - Google Patents

Abstract

This method is used to afford remote maintenance and supervision of point-to-point links, especially of the TRANSPAC centre/subscriber type, the data being exchanged between a centre modem MC and a subscriber modem MA by means of a data channel L. According to the idea of the invention, the data channel is also used to transmit the feedback test commands and the indications of change of state of the link. To do this, the transmission of data is interrupted by characteristic sequences of the said commands and indications, whilst the resending of the data is preceded by a so-called putting through sequence, the characteristic sequences being, of course, organised in such a way that the probability of identifying them in a data stream is very small. Application: remote maintenance of point-to-point data links.

Description

"METHOD OF TELEMAINTENANCE AND SUPERVISION OF BINDINGS
POINT A POINT ".

 The present invention relates to a method of remote maintenance and supervision of point-to-point links transmitting data by means of a data channel, including links of the type Center-Subscriber TRANSPAC, between a modem "Center" and a modem "Subscriber", method allowing from the "Center" modem to discriminate the different possible states of the link and to remotely control the test loop of the "Subscriber" modem.

Such a method is used to ensure the remote maintenance of modems such as for example the modem
SEMATRANS 1042 TRANSPAC Center commonly used in a TRANSPAC Center-Subscriber type link. Indeed in a point-to-point connection, it is advantageous that the modem "Center" on the one hand knows the states of the modem "Subscriber" and he can also transmit remote controls to said modem "Subscriber". For this a DC voltage of -48V emitted by the modem "Center" is superimposed on the data signal transmitted on the line. Depending on its state, the "Subscriber" modem regulates the line current from this voltage to different values which are chosen equal to 3mA and 6mA. The "Center" modem then detects one of the following four values: OmA, 3mA, 6mA,> 6mA. The "Center" modem is able to interpret the value detected as being related to a "Subscriber" modem fault or a transmission line fault or the unavailability of the modem "Subscriber" if it is for example performing a test. In addition, switching off the DC voltage from the "Center" modem puts the
"Subscriber" modem in test loop.

 The creation of a 48V voltage on the "Center" side, the current regulation on the "Subscriber" side and the detection of these currents require additional components, but these line access components are particular and rather expensive, which constitutes a first drawback. . A second disadvantage is further caused because a significant increase in current consumption is provided by the use of such a method. Indeed the increase in consumption can be of the order of 0.5W per modem "Center", which compared to the total consumption which is of the order of SW is not at all negligible.

 The present invention provides a method of the above kind but which does not have the disadvantages of the known method.

 For this purpose, the method for remote maintenance and supervision of links of the kind mentioned in the preamble is remarkable in that for transmitting the test loop commands and the indications of change of state of the link when an event occurs. on the link, characteristic sequences of said commands and indications are transmitted on the data channel in place of the data, the characteristic sequences used being organized in such a way that the probability of identifying them with a data stream is very small whereas the emission or the reissue, at the time of the disappearance of the event on the link of the data is preceded by a so-called sequence of putting in presence to ensure a perfect synchronization of the modems.

 Thus, thanks to the invention, it is possible to perform remote maintenance and telesupervision functions using a method in the loop rather than using an out-of-band method as is currently done. The dialogue thus established between the modem "Center" and the modem "Subscriber" makes it possible to make a diagnosis of the state of availability or unavailability of the line and this on the one hand without requiring additional components and on the other hand without an increase in consumption.

 With regard to the characteristic sequences, the codes used to transmit the event indications may be any to the reserve so that the probability of identifying them in the data stream is very low.

However, for purposes of efficiency and universalisation of the process according to the invention, it is advantageous to choose characteristic sequences already normalized by the
CCITT or by other bodies.

 The following description with reference to the accompanying drawing, all given by way of example, will make it clear how the invention can be realized.

 The single figure schematically shows a point-to-point connection using the remote maintenance and supervision method according to the invention. A point-to-point link enables the transmission of data from a source data processing terminal equipment ETTt.C located in a central station, therefore on the center side, to a terminal data processing terminal device ETTD.A located in a secondary station, therefore side subscriber through a transmission medium or data channel which is represented by the 2-wire line L. The adaptation of the digital signals to the medium and the regeneration of the data at the reception are provided by the center modem MC on the center side and the subscriber modem My subscriber side. The digital interfaces, ie the JC junction on the center side and the JA junction on the subscriber side, have the role of enabling the management and therefore the processing by the data terminal by ensuring the dialogue between the terminal and the modem. The digital interfaces used in the device for which the method according to the invention is implemented are described in the CCITT V24 notice. The various junction circuits useful for the implementation and apprehension of said method are given below.

 The circuit 105 gives the information 'request to transmit'.

 The circuit 166 gives the information Z ready to send ".

 The circuit 107 gives the information "Data station ready".

 The circuit 108 gives on the one hand the information 1: "Connect the data station on the line and on the other hand the information 2 X zEquipped data terminal equipment".

 The circuit 109 is the detector of the line signal received on the data channel.

 The circuit 122 is the detector of the signal received online on the return channel, used as a status indicator.

 The circuit 142 is the test indicator.

 In general, a remote maintenance and remote monitoring device must allow, from the central modem, on the one hand to remotely control the loopbacks of the subscriber modem and on the other hand to discriminate four possible states of the link.

 - state A: normal connection.

 - B state: subscriber modem unavailable, ie either unpowered or loopback.

 - state C: faulty subscriber modem or loopback commands made from the central modem, the disturbance being able to affect both the remote control and remote control transmission-reception part and the data transmission-reception part.

 - State D: faulty connection, ie cut or short-circuit line.

 The method according to the invention is intended to replace in all its functionalities, the remote maintenance by current TRANSPAC used until now.

 The principle used consists in generating a certain number of sequences which, using the data transmission channel by interrupting the transmission of said data from one end, are interpreted as a signaling message by the other end.

 For this purpose, very specific sequences are sent in place of the data, which sequences are preferably chosen already standardized by the CCITT. It is obvious that this choice is not limiting, however it brings the advantage of easy standardization.

 Thus according to a first choice, the characteristic sequences used are of the scrambler type V54 whose generator polynomial is 1 + x'4tx'7.

 According to a second choice, the characteristic sequences used are of the complement type of the jammer V54 whose generator polynomial is 1 + x-3 + x-7. This jammer is defined in the V33 notice.

The subscriber modem, in addition, can issue both types of signals
- Several 1 "in-line permanent scrambled non-scrambled biphase, referenced in the sequence" 1 "PNB, equivalent to a square frequency signal half the bit frequency.

 - signaling using a square-wave signal with a frequency of 1 kHz.

 The generation, transmission and supply of this signal must be performed independently of the data transmission channel.

 In addition, at the beginning of transmission or at the disappearance of the event that led to the generation of the characteristic sequences, therefore during the transition from an abnormal state to a normal state, a so-called conferencing procedure is performed to ensure perfect synchronization of modems.

 According to a preferred choice, the so-called presence sequence consists of a series of "1" permanent non-scrambled immediately transmitted after recognition and retransmission by the subscriber modem of a sequence of "1" scrambled type V33 previously issued by the center modem.

 Indeed, the center modem which then systematically has the role of caller begins therefore permanently emit a sequence of "1" scrambled type V33. The subscriber modem which was silent since the center did not emit me, detects a signal in line and then emits the same sequence of "1" scrambles of the type V33 and this during a time T corresponding to the sum of the convergence time tc of the echo canceller included in the modem and the scrambled 64 bits (approximately) to "1" tr recognition time of type V33 transmitted by the center modem. This is when the subscriber modem issues a series of "1" permanent ("1" PNB).

 The center modem detects 16 of these "1" PNBs and puts the circuit 109 in the working state by keeping the circuit 106 in the idle state. It then emits a sequence of 32 "1" PNB and switches the circuit 106 to the working state.

 The subscriber modem must then detect 16 bits at "1" out of the 32 transmitted by the center modem. After detection, it switches circuit 109 and circuit 106 at the same time to the working state.

The principles used to establish the different procedures are as follows
In the normal state (state A), the data channel is used in transparent mode for the user after a presentation procedure at the beginning of transmission or during a situation of return to normal operation.

At power up, the center modem therefore initiates the previously described presence procedure. The trunking circuits are then in the following states
- for the center modem
circuit 122 in the working state
circuit 142 at rest
circuit 109 in the working state
- for the subscriber modem
circuit 107 in the working state
circuit 142 at rest
circuit 109 in the working state
In states B, C, D, ie when an event occurs on the link, one of the modems must force the online transmission of a characteristic sequence to signal to the other modem abnormal event. After interpreting the received signal, the modem must react by indicating the state of the link on its interface V24.

 Thus, in state B for which the modem is unavailable, there can be four events. The first is related to the power loss of the subscriber modem.

When the subscriber modem is no longer powered, it transmits during the duration of the fall of the power supply a square signal of frequency approximately equal to 1 kHz, the junctions are then in the following states
- for the center modem
circuit 122 at rest
circuit 142 in the working state
circuit 109 at rest
- for the subscriber modem
circuit 107 at rest
circuit 142 at rest
circuit 109 at rest
The same procedure applies when the signal on the circuit 108 of the subscriber modem disappears, a 1kHz frequency signal is then emitted for about 100 ms.

The second event of the state B for which the subscriber modem is unavailable is relative to the disappearance of the signal on its circuit 105. The odes also transmits the signal of frequency 1 kHz for about 100 ms, then "1" PNB which cause the maintaining the circuit 109 of the modem center in the work1 state the junctions are then in the following states
- for the center modem
circuit 122 at rest
circuit 142 in the working state
circuit 109 in the working state
- for the subscriber modem
circuit 107 in circuit state 108
circuit 142 at rest
circuit 109 in the working state
The third event of state B for which the subscriber modem is unavailable occurs during the internal test called manual loop 3.

Before executing such a loop, the modem sends a 128 bit sequence of 0 "of type V33, the junctions are then positioned in the following states
- for the center modem
circuit 122 at rest
circuit 142 in the state 'work
circuit 109 at rest
- for the subscriber modem
circuit 107 in circuit state 108
circuit 142 in the working state
circuit 109 in the working state
The output of each of these states is effected by a putting procedure, the transmitting center modem, as soon as the unavailability is detected, a sequence of 1 "of the type
V33.

 The fourth event of the state B for which the subscriber modem is unavailable appears during the manual loop test 2 of the subscriber modem.

 Before executing this loop, the modem emits a 128 bit sequence of "0" of type V33. The center modem distinguishes this state from the previous one by the circuit 109 and abstains then from issuing a sequence of "1" of the type V33. The subscriber modem, at the end of the loop test 2, transmits a sequence of "1" of the V33 type which imposes the triggering of the linking procedure.

During the loop 2 test, the junctions are in the following states
- for the center modem
circuit 122 at rest
circuit 142 in the working state
circuit 109 in the working state
- for the subscribing modem
circuit 107 at rest
circuit 142 in the working state
circuit 109 at rest
In state C can present the following 6 events.

The first event relates to the transmission failure of the subscriber modem. At the appearance of this event the modem centers, on a fall of the signal of the circuit 109, interrogates the subscriber modem by sending on the line 64 "1" PNB. If the subscriber modem receives this interrogation, it responds by sending a signal at 1 kHz for approximately 100 ms. When the modem center detects this response the junctions are placed in the following states
- for the center modem
circuit 122 in the working state
circuit 142 in the working state
circuit 109 at rest
- for the subscriber modem
circuit 107 in circuit state 108
circuit 142 at rest
circuit 109 in the working state
If instead the center modem does not receive the response of the subscriber modem is that there is a line fault (see state D).

The second event relates to the failure to receive the subscriber modem. When this event occurs, that is to say on a fall of the signal of the circuit 109 'the subscriber modem transmits a sequence of "1 PNB in line, then it stops the transmission When the modem center detects this sequence the junctions are placed in the following states
- for the center modem
circuit 122 in the working state
circuit 142 in the working state
circuit 109 at rest
- for the subscriber modem
circuit 107 in circuit state 108
circuit 142 at rest
circuit 109 at rest
The third event appears on a loopback controller 2 that conforms to V54.The junctions are then in the following states
- for the center modem
circuit 122 in the working state
circuit 142 in the working state
circuit 199 in the working state
- for the subscriber modem
circuit 107 at rest
circuit 142 in the working state
circuit 109 at rest
When one of the last 3 events of state C appears, the center modem sends a sequence of "O" of type V33. The subscriber modem then stops broadcasting. The center modem positions its trunk circuits according to the state in which it is placed. The output of this state is effected by a linking sequence. The last three events of the state C are as follows
The fourth event relates to the unavailability of the center modem when it performs a so-called manual loop 3 test. The state of the junctions is then the following
- for the center modem
circuit 122 in the working state
circuit 142 in the working state
circuit 109 in the working state
- for the subscriber modem
circuit 107 in circuit state 108
circuit 142 at rest
circuit 109 at rest
The fifth event relates to the unavailability of the center modem when the signal disappears on its circuit 105. The state of the junctions is then the following
- for the center modem
circuit 122 in the working state
circuit 142 in the working state
circuit 109 at rest
- for the subscriber modem:
circuit 107 at rest
circuit 142 in the working state
circuit 109 in the rest state
The sixth event relates to the unavailability of the center modem when the signal disappears on its circuit 108. The state of the junctions is then as follows.
- for the center modem
circuit 122 in the working state
circuit 142 in the working state
circuit 109 at rest
- for the subscriber modem
circuit 107 in circuit state 108
circuit 142 at rest
circuit 109 at rest
The state D corresponds to a line fault (line cut or short-circuit) .The state of the junctions is then the following one
- for the center modem
circuit 122 at rest
circuit 142 at rest
circuit 109 at rest
- for the subscriber modem
circuit 107 in circuit state 108
circuit 142 at rest
circuit 109 at rest
The following table summarizes for the different states A, B, C, D, the state of the center modem junctions and that of the subscriber modem when the various events occur. In the table a sign + designates a working state, a sign - denotes a state of rest while the designation 108 means that the junction concerned is then in the state of the circuit 108. In addition, the reference HC designates the modem center and the reference MA the subscriber modem. Finally the term "OFF" symbolizes the disappearance of a signal on a circuit and the terms D.Em, D.Rec respectively indicate a transmission fault, a reception fault.

<tb><SEP> Modem <SEP> Modem
<tb> center <SEP> ss <SEP> subscriber
<tb> STATE
<tb> | <SEP> 122 <SEP> 142 <SEP> 109 <SEP> 1107 <SEP> 142 <SEP> 1091 <SEP>
<tb> A <SEP><SEP> state normal <SEP> + <SEP> - <SEP> + <SEP> + <SEP> - <SEP> +
<tb> B <SEP> 1. <SE> MA <SEP> no <SEP> powered <SEP> - <SEP> + <SEP> - <SEP> - <SEP> - <SEP> - <SEP>
<tb> or <SEP> 108 <SEP> MA <SEP>"OFF"<SEP> l <SEP><SEP> l <SEP> l <SEP>
<tb> | <SEP> 2. <SEP> 2. <SEP> 105 <SE> MA <SEP>"OFF"<SEP> I <SEP> - <SEP> + <SEP> + <SEP> | 108 <SEP> - <SEP> + <SEP> I <SEP>
<tb> t <SEP> 3. <SEP> MA <SEP> in <SEP> loop <SEP> 3 <SEP> Manual <SEP> | <SEP> | <SEP> - <SEP> - <SEP> + <SEP> - <SEP> | 108 <SEP> + <SEP> + <SEP> 1 <SEP>
<tb> 4. <SEP> MA <SEP> in <SEP> loop <SEP> 2 <SEP> Manual <SEP> - <SEP> + <SEP> + <SEP> - <SEP> + <SEP>
<tb> C <SEP> 1. <SE> MA <SEP> D.Em <SEP> + <SEP> + <SEP> - <SEP> 108 <SEP> - <SEP> +
<tb> 2. <SEP> 2. <SE> MA <SEP> D.Rec <SEP> I <SEP> + <SEP> + <SEP> - <SEP> J108 <SEP> - <SEP>
<tb> | <SEP> 3. <SEP> Remote control <SEP> loop <SEP> 2 <SEP> 1 <SEP> + <SEP> + <SEP> + <SEP> ss <SEP> - <SEP> + <SEP> - <SEP> I
<tb> 4. <SEP> 4. <SEP> MC <SEP> in <SEP> loop <SEP> 3 <SEP> Manual <SEP> | <SEP> + <SEP> + <SEP> + <SEP> + <SEP> 1108 <SEP> - <SEP> - <SEP> ss <SEP>
<tb> 5. <SEP> 5. <SEP> 105 <SEP> MC <SEP>"OFF"<SEP> I <SEP> + <SEP> + <SEP> - <SEP> I <SEP> - <SEP > + <SEP> - <SEP> ss <SEP>
<tb> | <SEP> 6. <SEP> 108 <SEP> MC <SEP>"OFF"<SEP> I <SEP> + <SEP> + <SEP> - <SEP> 1108 <SEP> - <SEP>
<tb> D <SEP> default <SEP> of <SEP> line <SEP> - <SEP> - <SEP> - <SEP> 108 <SEP> - <SEP>

 Thus in this method, the data channel is advantageously used for the transmission of characteristic data, well defined, in a given order, according to pseudo-random sequences, allowing effective monitoring of the state of the modems. In a similar manner to the notice t54 relating to the loop remote control 2 of a modem to a remote modem, the remote maintenance according to the present method interrupts the transmission of data from the terminals to substitute characteristic data corresponding to a state of the table remote maintenance shown above. It should be noted that such a method involving two basic loop modems such as those used in a TRANSPAC link has never been used, as well as the fact of signaling to the remote modem the test state of the modem. local has never been used in this type of modems.

Claims (4)

1. Method for remote maintenance and supervision of point-to-point links transmitting data by means of a data channel, including links of the type Center-Subscriber TRANSPAC, between a modem "Center" and a modem "Subscriber" allowing from the modem "Center" to discriminate the different possible states of the link and remote control looping tests of the modem "Subscriber", characterized in that, for transmit the test loop commands and the link state change indications when an event occurs on the link, characteristic sequences of said commands and indications are sent on the data channel in place of the data , the characteristic sequences used being organized in such a way that the probability of identifying them with a data stream is very low, whereas the transmission or retransmission, when the event on the link disappears, of the data is preceded by a so-called linking sequence to ensure perfect synchronization of the modems. 2. Method for remote maintenance and supervision of links according to claim 1 characterized in that the characteristic sequences used are of the scrambler type. V54 whose generator polynomial is 1 + x-4 + x-7. 3. The remote maintenance and supervision process according to claim 1, characterized in that the characteristic sequences used are of the complement type of the jammer V54 whose generator polynomial is 1 + x-3 + x-7. 4. Remote maintenance and supervision method according to one of the preceding claims, characterized in that the so-called interlocking sequence consists of a series of H "1" permanent uncurried immediately transmitted after recognition and retransmission by the subscriber modem a sequence of "1" scrambled type V33 previously issued by the center modem.