JPH09168054A - Method for detecting fault in transmission line of communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent production of a call loss even when a fault takes place in a transmission line in the communication system where a D-channel signal is sent between 1st and 2nd communication equipments via a primary group interface. SOLUTION: When no expiration of a timer T309 is discriminated in the confirmation as to whether or not the timer T309 expires, whether or not a fault takes place frequently is confirmed. In this case, it is preferable to confirm whether or not faults of a prescribed number of times or over take place within a prescribed time as criterion data to discriminate a fault of D-channel to be in a fixed fault. When it is confirmed that faults of a prescribed number of times or over take place within a prescribed time, an initial setup request of layer 3 is started and transmitted. On the other hand, when it is confirmed that faults of a prescribed number of times or over does not take place within a prescribed time, it is discriminated that the fault is not a fixed fault and a state notice or a state inquiry procedure is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention can be applied to a transmission path failure detection method for a communication system, for example, to a transmission path failure detection method for a D channel common line of a primary group interface accommodated in a digital private branch exchange.

[0002]

2. Description of the Related Art Generally, the D channel is also called a signal channel and is a channel for transmitting a control signal between a terminal-network and a terminal-terminal. By using this D channel, the usage of the leased line can be enhanced and diversified.

FIG. 2 is a configuration diagram of a communication system showing the concept of a D channel common line connection configuration example and the flow of transmission / reception signals. In FIG. 2, the communication system includes a digital private branch exchange (EPBX) A station and carrier MUX1 and a digital private branch exchange (EPBX) B station and carrier MUX2.
And are connected by transmission lines L1 and L2. The transmission lines L1 and L2 are D channel common lines of the primary interface.

In the structure connected by the D channel common line of the primary group interface as described above, the signaling carriage mechanism (SCM) is from the layer 1 to the layer structure for performing call control as shown in FIG. It is composed of layer 3 and is basically implemented by software that controls a standardized recommendation-compliant control unit from a call control application (CCAP) at the Telegraph and Telephone Technical Committee (TTC).

FIG. 4 shows an initial establishment sequence of the D channel common line. After Layer 1 is established, T
According to the TC standard, from station A (or station B) to layer 2 (D
SABME (Set As) to establish a channel
ynchronous Balanced Mode
Extended: Activates the setting of the multiframe link in the extended mode) Sends a frame. Station B (or A
The station) recognizes that the D channel is established (DL setting is displayed), and UA (Unnumbered Ack: SABME)
Or an acknowledgment response to DISC) frame is returned. A
The station (or B station) receives the UA frame and recognizes that the D channel is established (DL setting confirmation).

[0006] Further, the subsequent layer 3 initialization procedure is optional, and is T309 after D channel failure detection.
Start the timer (standard 90 seconds), and in the recovery within T309, state notification (STATUS) or state inquiry (S
Performing TATUS ENQ) is also specified as an option. In addition, Layer 1 standardized in TTC is standardized in Layer 2 under the environment in which the opposite station can transparently transmit the Layer 1 signal.

FIG. 5 shows a failure sequence on one side of the transmission path of the D channel common line. In this case, when used in an environment other than an environment in which layer 1 is transmitted transparently, station B normally looks long. Therefore, the call to station A is almost lost.

[0008]

As described above, according to the conventional technique, when the layer 1 of the D-channel common line is used in an environment other than an environment in which it is transmitted transparently, the station B normally looks for a long time. Therefore, there was a problem that the call to station A was almost lost.

Therefore, even if a transmission path failure occurs in a communication system in which a D-channel signal is transmitted by the primary interface between at least the first communication device (for example, exchange) and the second communication device, There has been a demand for providing a transmission line failure detection method for a communication system that does not cause a call loss as in the past.

[0010]

SUMMARY OF THE INVENTION Therefore, according to the present invention, there is provided a transmission path fault detecting method for a communication system in which a D channel signal is transmitted by a primary interface between at least a first communication device and a second communication device. In the above, the above-mentioned problems are solved by the following characteristic configurations.

That is, the transmission path fault detection method for a communication system of the present invention comprises a transmission abnormality presence / absence detection process for detecting the presence / absence of transmission abnormality of a D channel signal by one of the two communication apparatuses. When a transmission abnormality is detected, a timer is started, and a transmission abnormality determination process is performed to determine whether the transmission abnormality is frequently detected within a predetermined time. If it is frequently detected within
After the initial setting request signal is transmitted by the protocol, the initial setting request waiting process is performed.

By performing such processing, if a failure occurs frequently in the transmission line and the failure is frequently detected, the communication apparatus that has detected the failure sets it as a fixed failure during initialization. Therefore, even if a call signal from a lower-level device is given to this communication device, it is possible to prevent the call from being lost as it is, because it is processed during the initial setting.
By adopting the above-mentioned configuration for both of the two communication devices, it is naturally possible to reduce the call loss for the call signal from the lower device connected to both the communication devices.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment of the present invention will be described with reference to the drawings. In the present embodiment, the digital private branch exchange accommodating the D channel common line of the primary group interface has the reference data and the determination process for determining the D channel failure as the fixed failure, so that the failure on one side of the transmission path occurs. Even so, the digital exchanges on both sides can be blocked, and the D channel common line transmission path failure detection method is configured so that an effective network can be constructed including selection of a bypass route at the time of transmission.

In the D-channel common line connection in the digital private branch exchange of the present embodiment, reference data for determining a D-channel fault as a fixed fault is preliminarily used in order to perform processing at the time of D-channel common line fault / recovery detection. Configure to set. That is, as the reference data, specifically, a fixed time (for example, standard 5 minutes), a fixed number of times (for example, standard 5 times), and the like are set.

FIG. 6 is a diagram showing the configuration (a) and the fault sequence (b) of the D channel common line transmission line fault detection system. In FIG. 6, the D channel common line transmission line failure detection system is a digital private branch exchange (EPBX) A.
Office and carrier MUX1, digital private branch exchange (EPB
X) station B and a transport device MUX2. In such a system configuration, it is assumed that a failure occurs in L2 on the upstream transmission path from the B station to the A station.

Next, an outline of the operation of the D-channel common line transmission path failure detection method of the present embodiment will be described first. Upon detection of D channel failure, T309 timer is started and T3
Release the call in use at 09 timeout. When the D channel failure recovery is detected, if the T309 timeout or later, the layer 3 initialization request (RESTART) is activated, and the initialization confirmation (RESTART ACKnowle
dge: Recognize that the initial setting is being performed until the initial completion is notified).

If the T309 timeout is not exceeded, the D channel failure is determined based on the reference data for determining the fixed failure. If it is determined that it is not a fixed fault, status notification (STATUS) or status inquiry (STAT)
US ENQuery: Inquiry about the status of the other party) is performed, but when it is determined that a fixed failure occurs, the same operation as the D channel failure recovery after the T309 timeout is performed.

Next, FIG. 1 is an operation flowchart for explaining in detail the operation of the above-mentioned D channel common line transmission path failure detection method. In FIG. 1, first, when the digital private branch exchange (EPBX) A station detects a failure of the D channel, it starts a standard 90 second T309 timer (step S1) and releases the call in use at T309 timeout. Next, when the restoration of the D channel failure is detected (step S2), it is then confirmed whether or not the T309 has timed out (step S3).

If it is determined that the T309 has timed out after this confirmation, the digital private branch exchange (EPBX) B station then activates and transmits a layer 3 initialization request (RESTART) (step S5). Next, a digital private branch exchange (E
PBX) Station B confirms the initial setting (RESTART AC
K) is received and it is recognized that the initialization is in progress (step S
7).

A characteristic of this embodiment is that
When it is determined that the T309 has not timed out (step S3) and whether or not the T309 has timed out, it is confirmed whether or not a failure frequently occurs (step S4). That is, it is preferable to confirm whether or not a failure has occurred a fixed number of times (standard 5 times) or more within a fixed time (standard 5 minutes) as reference data for determining a D channel failure as a fixed failure (step S).
4).

With this confirmation, the above-mentioned fixed time (standard 5 minutes)
If it is confirmed that the failure has occurred a certain number of times (standard 5 times) or more, the layer 3 initialization request (REST
The ART) is activated and transmitted (step S5). on the other hand,
In the above confirmation, when it is confirmed that the failure has not occurred more than a certain number of times (5 times as standard), it is determined that the failure is not a fixed failure, and status notification (STATUS) or status inquiry (S).
The TATUS ENQuery procedure is performed.

Next, description will be made with reference to the failure sequence diagram on one side of the transmission path shown in FIG. In FIG. 6 (b), first, layer 1 is established between the digital private branch exchange A station and the digital private branch exchange B station (step S10). Next, the digital private branch exchange A station transmits the SABME signal at layer 2 to the digital private branch exchange B station (step S1).
1). After receiving the SABME signal, the digital private branch exchange B station transmits the UA signal at layer 2 to the digital private branch exchange A.
It transmits to the station and establishes the D channel (step S12).

However, this UA signal cannot be given to the digital private branch exchange B station because the upstream transmission line L2 has a failure. Therefore, when the digital private branch exchange A station judges T200 timeout, the SABME signal is transmitted again to the digital private branch exchange B station at layer 2 (step S13). As a result, the digital private branch exchange B station receives the SABME signal again, and then transmits the UA signal to the digital private branch exchange A station at layer 2,
The D channel is established (step S14). When the digital private branch exchange A station determines T200 timeout, it transmits the SABME signal to the digital private branch exchange B station again in layer 2 (step S15).

As a result, the digital private branch exchange station B
After receiving the SABME signal again, the UA signal is transmitted to the digital private branch exchange A station in Layer 2 (step S16). Then, since the upstream transmission path L2 has a failure, it is not given to the digital private branch exchange B station, and the digital private branch exchange B station receives the initial setting request (REST
The ART) is activated (step S17). As a result, it can be determined that the D channel common line route for the digital private branch exchange B station is being initialized.

FIG. 7 is a hardware block diagram of an example of a digital private branch exchange for realizing the above-mentioned D channel common line transmission path failure detection method of FIG. In FIG. 7, the digital private branch exchange mainly includes a time division switch circuit (TSW) 20, a control unit 25, and subscriber circuits LC1 to LC1.
Lcn, repeater circuit (POT) 23, ISDN primary group interface trunk (PRI) 21, and ISDN
It comprises a basic interface trunk (BRI) 22.

In the operation flow chart of FIG. 1 described above, reference data (step S4) for determining a D channel fault as a fixed fault is, for example, in the main memory of the control unit 25 in the hardware configuration diagram of FIG. 27 is preferably set as one of the station data. Then, the reference data for determining the D channel fault set in the main memory 27 as the fixed fault is fetched by the access from the CPU 26 and used for detecting the D channel common line transmission line fault.

The functions and operations of the other constituent circuits of the digital exchange of FIG. 7 are described in JP-A-5-1149.
No. 41 (for example, the description of FIG. 4 of the remote maintenance system of the digital private branch exchange system) is disclosed, and a practical device can be realized with these configurations.

(Effects of the Embodiment of the Present Invention): According to the above-described embodiments of the present invention, reference data for determining a D channel failure as a fixed failure in the processing method at the time of D channel common line failure / restoration detection. (For example, fixed time (standard 5 minutes),
By a method of combining a certain number of times (standard 5 times, etc.) and the initial setting procedure of Layer 3 that can confirm the bidirectional normality of the transmission line at the time of judgment, the corresponding D.P in the opposite digital private branch exchange (Station A / B) It is possible to block the channel common line route.

If the D channel signal transmission abnormality is not frequently detected within the predetermined time, the status notification processing or status inquiry processing is performed to the partner digital private branch exchange by the layer 3 protocol, which is not fixed. In the case of a temporary abnormality, the status notification processing or the status inquiry processing can be continued.

Further, in determining whether or not the D-channel transmission abnormality is frequently detected within a predetermined time, reference data for determining whether or not the D-channel signal transmission abnormality is a fixed fault is prepared in advance. By setting in the memory circuit and making the above determination based on this reference data, the determination can be made with a very simple configuration.

Therefore, even when the layer 1 of the D channel common line is used in an environment other than the environment in which it is transmitted transparently by the above-described configuration, the time normally seen from the station B is long, and therefore the station A is transmitted to the station A normally. It is possible to solve the problem that the outgoing call is almost lost, and a transmission path failure occurs between the digital private branch exchange A station and the digital exchange B station in the communication system in which the D channel signal is transmitted by the primary group interface. However, it is possible to prevent the call loss from occurring as in the conventional case.

(Other Embodiments) (1) FIG. 8 shows a call from station B to station A in a network in which station C is a detour route between station A and station B of the digital private branch exchange. FIG. 3 is a system configuration diagram for bypassing and connecting to station C. In FIG. 8, a transport device MUX1A,
A transmission line L3 is newly provided between the transport device MUX2B and the digital private branch exchange C station and the transport device MUX3.

When a fixed fault has occurred in the transmission line L2, the digital private branch exchange B station is in the process of initial setting by the above-mentioned D channel common line transmission line fault detection method of FIG. Instead of transmitting directly to the A station, it transmits to the digital private branch exchange C station and the carrier MUX3 for detour transmission through the transmission line L3. Upon receiving this signal, the digital private branch exchange C station indirectly transmits the data to the digital private branch exchange A station through the transmission line L3 to indirectly connect the digital private branch exchange B station and the A station via the digital private branch exchange C station. It is possible to enable the transmission of channel signals.

(2) Furthermore, a transmission line failure occurs even in a usage mode other than the environment in which the D channel common line is accommodated in the digital private branch exchange and the layer 1 is transmitted transparently (the same control is possible under the environment). Sometimes effective operations can be performed.

(3) Further, in FIG. 6 (a), the transport devices MUX1 and MUX2 are used, but other DSUs are used.
It can also be applied to the case of transmission by (Digital Service Unit).

(4) Also, digital private branch exchanges A and B
A station, a station C, etc. can also apply a packet switch, a voice mail device, an ISDN communication device, etc.

[0037]

As described above, the present invention provides a transmission line fault detection method for a communication system in which a D channel signal is transmitted by a primary interface between at least a first communication device and a second communication device. Any one of the two communication devices detects a transmission abnormality presence / absence detecting process for detecting the presence / absence of a transmission abnormality of the D channel signal, and starts a timer when the transmission abnormality is detected, and the transmission abnormality is detected for a predetermined time. If a transmission abnormality determination process is performed to determine whether or not the transmission abnormality is frequently detected within a predetermined period, and if the transmission abnormality is frequently detected within a predetermined time period, the layer is transmitted to the other communication device. After the initial setting request signal is transmitted by the three protocols, the initial setting request waiting process is performed.

By adopting such a configuration, at least a communication path in which a D channel signal is transmitted by the primary interface between at least the first communication device (eg, exchange) and the second communication device is a transmission line. Even if a failure occurs, it is possible to realize a transmission line failure detection method for a communication system, which does not cause a call loss as in the conventional case.

[Brief description of the drawings]

FIG. 1 is an operation flowchart of a D channel common line transmission path failure detection method according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional D channel common line transmission system.

FIG. 3 is a block diagram of a hierarchy for D channel common line call control in a conventional example.

FIG. 4 is an explanatory diagram of a D channel common line initial establishment sequence of a conventional example.

FIG. 5 is a diagram of a transmission line one-sided failure sequence of a D channel common line in a conventional example.

FIG. 6 is a diagram of a transmission line one-sided failure sequence of the D-channel common line according to the embodiment.

FIG. 7 is a hardware configuration diagram of the digital exchange according to the embodiment.

FIG. 8 is a configuration diagram of a detour system when a D-channel common line fails in another embodiment.

[Explanation of symbols]

A, B, C ... Digital private branch exchange, L1, L2, L3 ...
Transmission line (D channel common line), MUX1 to MUX3 ... Carrier device.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H04Q 3/58 101 H04L 13/00 313

Claims (4)

[Claims] 1. A transmission path failure detection method for a communication system in which a D-channel signal is transmitted between at least a first communication device and a second communication device by a primary group interface, the method comprising: One of the communication devices detects the transmission abnormality of the D-channel signal, detects whether there is a transmission abnormality, and starts a timer when the transmission abnormality is detected, and whether the transmission abnormality is frequently detected within a predetermined time. If the transmission abnormality is frequently detected within a predetermined time in the transmission abnormality determination processing for determining whether or not the transmission abnormality determination processing is performed, the other communication device is notified of the initialization request signal by the layer 3 protocol. A transmission path failure detection method for a communication system, comprising: initial setting request processing for performing initial setting confirmation waiting processing after transmission. 2. If the transmission abnormality is not frequently detected within a predetermined time, then a state notification process or a state inquiry process is performed on the other communication device by a layer 3 protocol. A transmission line failure detection method for a communication system according to claim 1. 3. In determining whether or not the transmission abnormality is frequently detected within a predetermined time, reference data for determining whether or not the transmission abnormality of the D channel signal is a fixed fault is stored in a memory in advance. 3. The transmission line fault detection method for a communication system according to claim 1, wherein the determination is made based on the reference data set in a circuit. 4. In addition to the two communication devices of the communication system, another communication device is connected by a primary interface, and D
When a channel signal is transmitted and a transmission path failure is detected between the transmission paths of the two communication devices, after performing the initialization request process, the layer is transmitted to the other communication device. 4. The D channel signal is transmitted between the two communication devices by transmitting the D channel signal according to the 3 protocol and passing through the other communication device. Method for detecting transmission line failure in communication system of the above.