MXPA97009592A - Method and system to identify defalla locations in a communication network - Google Patents

Abstract

The present invention relates to a communication network having a plurality of nodes and a plurality of communication circuits interconnecting said nodes, each of said nodes having detected along a communication circuit a fault signal originated by a fault in said communications circuit, a method for each said node along said communication circuit to identify the location of said failure in said circuit, comprising the steps of: periodically transmitting a fault location identifier originated by each said node on said communications circuit, stopping the transmission of said originating fault identifier originated until another identifier or a normal signal is received from an upstream node, and confirming that said originated fault location identifier is representative of the correct location of said failure if said location identifier of failure originated until another identifier or a normal signal is received from an upstream node, and confirming that said originating fault identifier originated is representative of the correct location of said failure if said originated fault location identifier was sent at least one number of times predetermined

Description

METHOD AND SYSTEM TO IDENTIFY FAILURE LOCATIONS IN A COMMUNICATIONS NETWORK Related Requests This invention also relates to a request for. Russ entitled "Systems and Method for Resolving Subtancially Simultaneous Bi-directional Requests of Spare Capacity" ("Systems and Methods for Solving Substantially Simultaneous Bidirectional Demands of Available Capacity") (RIC-95-009), assigned to the same assignee as this invention and presented concurrently with the present having the serial No.. This invention also relates to a request from Russ and Cois; entitled "Automated Path Verification for SHN-Based Restoration" ("Verification of the Automated Trajectory for Resetting on the Basis of SHN") (Case No.RIC-95-010), assigned to the same assignee of the present invention and filed concurrently with the present, having the serial No.. This invention also relates to a request for. Russ entitled "Automated Restoration of Unrestored Link and Nodal Failures" ("Automated Restoration of a Non-Reestablished Link and Nodal Failures") (Case No. RIC-95-059), assigned to the same assignee of the present invention and filed concurrently with the present having the serial number. This invention still further relates to a request from Russ and Cois; entitled "Method and System for Resolving Contention of Spare Capacity Circuits of a Telecommunications Network" ("Method and System to Resolve Obstruction of Circuits with Available Capacity of a Telecommunications Network") (Case No. RIC-95-005), assigned to the same assignee of the present invention and filed on June 6, 1995, having the serial No.. FIELD OF THE INVENTION The present invention relates to a telecommunications network having a plurality of intelligent nodes interconnected by a plurality of intervals to have a plurality of communication circuits, and more specifically to an access path to identify the location of the failure in the case of a failure in one or more of the communications circuits or intervals in the network, without resorting to a central system for the diagnosis of the failure. BACKGROUND OF THE INVENTION At any time a description such as a fiber cut occurs in a communications network having a plurality of nodes interconnected by means of a plurality of communication intervals to have a plurality of communication circuits, odd signals representative of the rapid description propagated in a wide area of the network, beyond the point of failure. This spread makes it difficult to identify the location of the fault. But to divert traffic from communications circuits around the fault, it is necessary to identify the point of failure. Frequently, such identification is carried out by means of a central network management system by means of a sophisticated analysis of the alarm messages received from the affected nodes, coupled with the topology information of the network stored in the central system. However, such a centralized access path for the location of the fault is relatively slow and the possible restoration of disorganized communication traffic to normal operation is often delayed. With the increasing deployment of the intelligent elements of the network, such as the digital interconnection systems, in the nodes of the current communication networks, it has been possible to carry out the identification of the failure described above, and the subsequent restoration of traffic disorganized to a faster normal operation using distributed techniques instead of centralized methods. One such distributed method for locating a faulty range is described in the United States Patent of Pekarske 5,233,600. Pekarske teaches a method according to which, when an interval in a network fails, the two nodes at each end of the faulty interval could identify, which are the nodes belonging to the faulty interval, without the help of a central system,. The other nodes affected by the interval failure could also identify that the intervals, to which they are directly connected, are not the source of the failure. This identification is based on the monitoring of each circuit in a given interval for either a directly observable signal abnormality or an alarm indication signal. An inactive signal is sent as soon as a directly observable abnormal signal or an alarm indication signal is detected. And immediately it is declared that the upstream channel from the node has failed when either the abnormality of the directly observable signal or the alarm indication signal is received for a period of time greater than that predetermined. Being able to identify the faulty interval in the manner described in Pekarske is sufficient to carry out a procedure for restoring the distributed link (which is limited to the diversion of traffic from the disorganized communication circuits), by means of the two nodes belonging to the faulty interval. However, a shortcoming of Pekarske's method is that knowledge of which specific interval has failed is limited to those two pertaining nodes. In other words, the other nodes in the network affected by the failure would not have knowledge of the identity of the faulty interval. Still for the purpose of performing a more efficient restoration technique, which could be referred to as a distributed path restoration technique to restore each disorganized communication circuit independently of the other disorganized circuits, other information such as the identity of the two nodes contiguous that join in the damaged segment of the communication circuit also needs to be known to all nodes in the network. One of the reasons why the technique of resetting the distributed trajectory is preferred over the link restoration method is that the first can potentially explore a much larger number of reset options than the latter. Another reason is that the distributed path restoration technique potentially requires a smaller amount of available capacity in the network than the distributed link restoration technique, to provide the same level of capacity in restoring the network.

SUMMARY OF THE INVENTION The present invention relates in general to disclosing to all nodes of a telecommunications circuit the location of a fault in a communication circuit of malfunction in the network. The communication network of the present invention comprises a plurality of intelligent nodes interconnected by a plurality of communication intervals to have a plurality of communication circuits. For the present invention, the intelligence in the nodes, as well as in the devices in the intervals, can detect abnormalities of the signal in the communication circuits. These abnormalities in the signal can be represented by a signal loss (LOS) or an alarm indication signal (AIS). The intelligence of the nodes can also convert an LOS into an AIS, and reformat the abnormal output signal when necessary in order to alert the nodes downstream that an upstream malfunction has been detected. When a communications circuit begins to malfunction, the resulting abnormal signal generally propagates along the entire length of the circuit before the nodes on the circuit have an opportunity to react to it. Consequently, once an abnormality of the incoming signal is detected, each node on the circuit assumes first that the deteriorated segment of the circuit is immediately upstream of it. The nodes then begin to periodically transmit to the nodes downstream a fault or identification identifier, which informs the nodes downstream that the faulty segment of the circuit is immediately upstream from the node. Periodic transmission of the fault identifier continues until the node itself is not the receiver of a similar identifier from another upstream node. And if the node continues to transmit its fault identifier to its nodes downstream at least a predetermined number of times, then the node would assume that it has correctly identified the location of the fault as specified in its identified failure. On the other hand, if a node receives a fault location identifier from an upstream node before it has finished sending its own identifier a predetermined number of times, it would suspend the sending of its own fault identifier. Instead, the node would register the received failure identifier. Furthermore, if a node receives the same fault identifier a predetermined number of times from an upstream node, it would assume that the received failure identifier contains the correct location of the fault.

Extending this method to all nodes on a malfunctioning communications circuit means that each node in that circuit can identify the correct location of the fault. The fault location identification process of the present invention is suspended by all nodes, and the circuit is considered to have returned to normal operation, if an incoming signal returns to a normal condition during the process. The fault location identifier may include data to identify the node that originates the identifier. It can also include information to identify the contiguous node that joins the circuit malfunction segment. By following the detection of the abnormality of the incoming signal, a node can reformat its output signal to alert its downstream nodes that a fault has been detected upstream of them. The fault location identifier can be transmitted in the form of a message. The signal formats specified in the American National Standards Institute (ANSI), the standards for the Synchronous Optical Network (SONET) and for the Digital Service Level 3 signals (Digital Service Level 3), (DS-3) can be used to reformat the abnormal output signal and derive a message channel from the supplementary bits to transmit the fault location identifier. According to the aboveIt is an object of the present invention to enable all nodes of a malfunctioning communications circuit in a communications network to learn the location of the fault that causes the malfunction of the circuit. Another object of the present invention is to enable each node of a malfunction communications path to identify which pair of contiguous nodes from the plurality of nodes of the path join the range containing the fault. BRIEF DESCRIPTION OF THE FIGURES Other objects and additional advantages of the present invention will be more apparent and the invention will be better understood by reference to the following description of a preferred embodiment of the invention taken in conjunction with the accompanying drawings, wherein: Figure 1 is an illustration of a simplified communications network used to explain the present invention; Figure 2 is a diagram illustrating a range of communications in the network of Figure 1; Figure 3 is a simplified diagram illustrating the SONET format for the payload of communications and overhead traffic; Figure 3a illustrates in more detail the SONET path overload components essential for the process of the present invention; Figure 4 is a flow chart describing the process steps of the present invention; and Figure 5 shows the format of a message used to identify the location of failure to other nodes. DETAILED DESCRIPTION OF THE INVENTION The illustrated in Figure 1 is an exemplary telecommunication network having nodes 12, 14, 16, 18, 20, 22, and 24 interconnected by various intervals 42A to 42K. Each of the nodes 12, 14, 16, 18, 20, 22, and 24 may comprise an intelligent element of the network such as an interconnect switch. Although not shown, each switch has a processor, its associated memories and data storage means, and the necessary ports that include the detectors to make the connection to the other switches in the adjacent nodes. In this way, each node is able to detect an abnormality of the incoming signal or an incoming alarm indication signal (AIS). In addition, each node can send an AIS to its nodes downstream and achieve other processing functions to identify a fault location. In addition, each node can make a decision that a detected failure is in fact not a real failure. For example, the detected fault may actually be a defect. An exemplary interconnect switch is the 1633-SX model developed by Alcatel Network Systems, Inc. Each of the 42A to 42K ranges, such as represented by the range 42A shown in FIG. 2, has a line termination equipment. conventional (LTE) 30 and 32 interconnected via a communication link 31 such as for example a fiber. LTE 30 in turn is shown to be connected to node 16 and LTE 32 to node 18. When the distance between LTE 30 and LTE 32 exceeds the equipment manufacturer's specifications for LTE, one or more repeaters may be needed to insert between them. For simplicity, such repeaters are not shown in Figure 2. There are multiple communication channels in the 42A range. These channels are derived from the subdivision of the transmission capacity of the LTEs. For example, a Level 48 Optical Carrier SONET LTE (OC-48) can provide 48 channels of Level 1 Synchronous Transport Signal (STS-1) communications. In each interval 42A to 42K, some or all of the communication channels are traffic channels, through which the communications traffic crosses between the nodes connected by the interval. Any of the remaining communication channels are kept in reserve as available channels. When there is a fault in the network, the available channels are put into service so that the disorganized traffic can be diverted. As mentioned before, LTE 30 and LTE 32, for the understanding of this invention, are supposed to be intelligent devices each capable of detecting the abnormalities of the incoming signal or the AIS, and sending the AIS. According to the foregoing, with reference to Figure 2, if an abnormality of the signal or a fault occurs between LTE 30 and LTE 32, such as at point 92, then LTE 30 would send an AIS to node 16. Similarly, LTE 32 would send an AIS to node 18. However, if the abnormality of the signal occurs at point 90, then both node 16 and LTE 30 would detect a loss of signal (LOS). As a result, each node 16 and LTE 30 send an AIS in the direction away from the fault. Similarly, if there is an abnormality of the signal at point 94, then both node 18 and LTE 32 would detect the abnormal signal and send the respective AIS in the direction away from the point of failure. The AIS and LOS discussed herein are supported through the communication channels affected by the failure. For the embodiment of the present invention in figure 1, several traffic channels are displayed. For example, traffic channel 60 transports traffic between nodes 12 and 14, traffic channel 62 carries traffic between nodes 14 and 16, traffic channel 64 carries traffic between nodes 16 and 18, etc. Other traffic channels shown in Figure 1 are 66, 68, 70, 72, 74, and 76. To simplify matters, the available channels are not shown in Figure 1. For the purpose of this invention, each " contiguous nodes, adjacent nodes, or nodes belonging to "a traffic channel (or a range) are defined as the pair of nodes that join or intersperse the traffic channel or the interval. It would also be appreciated that each of the nodes had prior knowledge of their nearby nodes. Also shown in the network of Figure 1 are the communications circuits 80, 82, and 84. For the present invention, a communication circuit, or path, is defined to have a plurality of traffic channels to transport traffic between a node endpoint and the other end node in the network. As shown, each communication circuit interconnects a traffic channel from each of a selected group of contiguous intervals through its intervention nodes starting with one end node and ending with the other end node in such a way that it does not form cycles. For example, the communication circuit 80 comprises, in sequence, an end node 12, a traffic channel 60, an intermediate node 14, a traffic channel 62, an intermediate node 16, a traffic channel 64, an intermediate node 18. , a traffic channel 66, and finally an end node 20. The communication circuit 82 in Figure 1, similarly comprises the end nodes 14 and 22, the intermediate nodes 16 and 18, and the traffic channels 72, 74 , and 76. Similarly, the communication circuit 84 between the end nodes 12 and 22 is installed and shown in FIG. 1. It is assumed here that each traffic channel, and the circuit therein used in the network of Figure 1, it is adaptable to transport bidirectional communications traffic. It is further assumed for the purpose of this invention that the communication channels belonging to each interval 42 can be grouped into packets, for example based on certain physical considerations of the range. The communications traffic transported by a communication circuit, for example the communications circuit 80 in FIG. 1, is organized into payload bits and supplementary bits according to the format specified in the applicable standard implemented in the network. An exemplary format illustrated in Figure 3 is based on the SONET standard specified by the American National Standards Institute (ANSI), in the T1.105-199x standard entitled "American National Standard for Telecommunications - Digital Hierarchy - Proportions of the Optical Interface and the Specification of the Formats (SONET) ". According to this format, each structure of the signals transmitted by a communication circuit in an STS-1 format over a period of 125 microseconds has a traffic payload section 310 of 774 byte sequences, a path overload section ( POH) 312 of 9 bytes, and a supplementary transport section 314 of 27 bytes. Under normal operating conditions each structure carries the actual communication traffic in payload 310, and the appropriate supplementary information in POH 312 and supplementary transport 314. POH 312 is further detailed in Figure 3a by having a growth byte which Z4 is not being used in 334 and one serial connection byte Z5 in 336. The use of byte Z4 in 334 and byte Z5 in 336 in the present invention will be more apparent, in the end. Under failure conditions, the procedure specified in the ANSÍ TI .105-05-1994 standard entitled "American National Standard for Telecommunications - Synchronous Optical Network (SONET) - Maintenance of the Serial Connection" can be invoked. According to this procedure, if a node detects an incoming AIS or an incoming abnormal signal, it would alert its downstream nodes that there is an upstream signal failure by transmitting an indication of incoming signal failure (IFS) of the same. Bits 1-4 of the Z5 byte in 336 are asserted, or converted, to a different state, for example from 0S to ls in the IFS. In order to maintain the object of the present invention, other steps of the signal reformatting procedure according to the SONET standard of the ANSI are not described herein. Based on the above-mentioned SONET formats of the ANSÍ, for the present invention, the process of identifying the fault location in a communications circuit in the network is discussed with reference to the flow chart of Figure 4. The process begins in the block 402 where a first node detects an abnormality in the incoming signal on a communication circuit by receiving either a loss of signal (LOS) or an AIS. Once an incoming LOS is detected by the node, it is converted or changed to an output AIS signal in block 404, and transmitted to the nodes downstream of the nodes originating from AIS. On the other hand, if an incoming AIS is detected, the node in block 406 is checked to determine if an ISF is also received. If an ISF is not received in 406, or after an incoming LOS has been converted to an AIS in 404, the node affirms an ISF over the output signal in block 408. The node at the beginning assumes that the segment of malfunction of the circuit is immediately upstream thereof and according to the above sends an identifier or identification of the fault location to the nodes downstream in block 410. In block 412 a check is made to determine if or not the fault location identifier has been sent downstream a predetermined number of times. If the answer is yes, then in block 414 the node confirms that the fault location identifier that actually originated it, indicates the correct failure location. If the answer is no, the process returns to block 406. Although not shown explicitly in Figure 4, the transmission of the same fault location identifier in block 410 could be done periodically with a delay in time, arbitrary between two transmissions Consecutive If an incoming ISF is detected in block 406, the process of identifying the fault location proceeds to register the identifiers of the incoming contiguous nodes in block 416. If a fault location identifier is received from a water node above, it is passed and the node suspends the sending of its own fault location identifier originating downstream. A check is made in block 418 to determine whether or not the same fault location identifier has been received by the node a predetermined number of times from the upstream node. If the answer is yes, then the confirmation is held by the node in block 420 that the location identifier of the fault in question truly indicates the correct location of the fault. If the answer is no, the process returns to block 416. Although not shown explicitly in Figure 4, the incoming signal is continuously monitored. And if the signal becomes normal before the failure location is confirmed, then the fault location identification process is suspended under the assumption that the abnormality of the signal may have been caused by a temporary signal defect. The fault location identifier may contain an indication to confirm the identity of the node that originates the identifier, or may contain an indication to confirm the identity of the node that originated the identifier as well as its contiguous node, which joins the segment of bad operation of the circuit.

In addition, the fault location identifier can be transported in a message format. Such a format for a fault location identifier message is illustrated in the. FIG. 5 where the node originating the identifier message is shown as node 1 at 502 and the junction of the node adjacent to the faulty circuit segment as node 2 at 504. The above-mentioned fault location identifier messages can be transmitted on a channel of message derived from the supplementary part of the transmitted signal, such as when using the byte that is not currently used Z4 previously shown as 334 in Figure 3a. The operation described in Figure 4 is further illustrated with reference to the network of Figure 1 herein. It is assumed that each node in the network of Figure 1 monitors the communication circuit (s) that passes through it. It further assumes that the interval 42A has failed at point 92. The traffic channels 64 and 74, and their respective communication circuits 80 and 82 according to the above are disorganized. The following discussion of the fault location identification process focuses only on a communications circuit 80. As the traffic channel 64 is monitored by each of the nodes 16 and 18, the process begins when the nodes 16 and 18 detect each One the abnormal signal. It is assumed that the abnormal signal detected at nodes 16 and 18 is an AIS. This AIS rapidly propagates throughout the communications circuit 80 and, in addition to the nodes 16 and 18, it can also be observed by the nodes 14, 12, and 20. Each of the nodes 12 to 20 of the circuit 80 will verify an ISF and , the defect of detecting such, affirms the AIS in an exit IFS. Additionally, each of the nodes 12 through 20 can first assume that the fault is in the circuit segment immediately upstream thereof and according to the above can send a fault location identifier to their downstream nodes. For example, node 16 will send an identifier 16-18 to node 14; and node 14, before receiving the identifier from node 16, could itself send an identifier 14-16 to node 12. Node 12, which is an end node of circuit 80, can terminate the signal. Similarly, node 18 will send an identifier 18-16 to node 20. Node 20, which is the other end node of circuit 80, can also terminate the signal. Once the identifier 16-18 from node 16 was received, node 14 will register it and pass it downstream. In addition, node 14 will cease transmission of its own output identifier, for example 14-16, in its output signal. Meanwhile, node 16 continues to transmit its identifier 16-18 downstream. After it transmitted the identifier 16-18 a predetermined number of times, for example 3 times, a confirmation is made by the node 16 that the identifier 16-18 is truly representative of the correct location of the fault. Similarly, nodes 14 and 12 will each arrive at the same conclusion after having received the same identifier, i.e. 16-18, a predetermined number of times, for example 3 times. Similar to the process described above, on the other side of interruption 92, nodes 18 and 20 will each also come to the conclusion that the correct location of the fault is given by means of identifier 18-16. If the failure point 92 is such that each nodes 16, 14, and 12 first detect an LOS, then the fault identification process is similar to the process described above with the exception that each nodes 16 and 14 will first convert the LOS into an AIS before asserting the ISF to an output AIS signal. By using the fault identification process described above, each of the nodes 14, 16, 18, and 22 can similarly determine, from the fault location identifier transmitted respectively to them, that the output for the communication circuit 82 is located between nodes 16 and 18. The method of identifying the location of a fault described above can also be applied to a communications network that carries the signals of the Digital Signal Level 3 (DS-3) according to the formats specified in the standard entitled "ANSI IT I07a-1989". For the DS-3 standard, to alert the nodes downstream of a malfunction of the upstream circuit, an AIS is replaced with an IDLE signal in step 408 of FIG. 4. In addition, the messages of the fault location identifier may be sent through, example, the X bits in the supplementary signal when the intelligence in the node and the interval equipment is specifically designed to handle it. In addition to identifying the two nodes that join at the point of failure, a fault location identifier can also identify the range of a plurality of intervals in the network that is the source of the failure. For example, as previously described, the junction at 92 in FIG. 1 would be located with any of the identifiers 16-18 or 18-16, each of which indicates the fault that is in the interval 42A between the nodes 16 and 18. In another embodiment of the present invention it would be possible to identify the location of the fault without the need to reformat the signal to alert the nodes downstream of the incoming signal failure. While the principles of the present invention have been described in terms of various embodiments in the above discussion, the invention is not limited to the specific embodiments set forth above but only by the scope of the invention as defined in the appended claims.

Claims (51)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and therefore the property described in the following claims is claimed as property. 1.
2. In a communications network having a plurality of nodes and a plurality of communication circuits interconnecting said nodes, each of said nodes having detected along a communication circuit a fault signal caused by a fault in said communication circuit, a method for each said node along said communication circuit to identify the location of said failure in said circuit, comprising the steps of: periodically transmitting a fault location identifier originated by each said node on said communication circuit; stopping the transmission of said originating fault identifier originated until another identifier or a normal signal coming from an upstream node is received; and confirming that said originating fault location identifier is representative of the correct location of said failure if said originating fault location identifier is sent at least a predetermined number of times.
3. The method according to claim 1, characterized in that it further comprises the steps of: detecting any incoming fault location identifier; confirming that any said detected fault location identifier is representative of the correct location of said failure when the same identifier receives said predetermined number of times and no abnormal signal is received before the last of said predetermined number of times.
4. The method according to claim 1, characterized in that it further comprises the step of: determining that there is no failure in said communication circuit if a normal signal is received before said confirmation step.
5. The method according to claim 2, characterized in that it further comprises the step of: determining that there is no failure in said communication circuit if a normal signal is received before any of said confirmation steps.
6. The method according to claim 1, characterized in that said transmission step further comprises the step of: providing said fault identifier with an indication that identifies one of the nodes joining said fault along said communication circuit.
7. The method according to claim 1, characterized in that said transmission step further comprises the step of: providing said fault identifier with an indication in a respective manner of identifying both nodes that connect said fault along said communications circuit.
8. The method according to claim 1, characterized in that, after each said node has detected said failure signal, said method further comprises the step of: reformatting said fault signal to another fault signal in such a way that the water nodes below said node are informed of said failure when the other said fault signal is diffused in them.
9. The method according to claim 7, characterized in that said fault signal is an Alarm Indication Signal (AIS) of Level 1 Synchronous Transport Signal (STS-1), said step of reformatting further comprising the step of: confirm said AIS in an Incoming Signal Failure (ISF) signal.
10. The method according to claim 7, characterized in that said failure signal is a Digital Service Level Alarm Indication Signal (AIS) of Level 3 (DS-3), said step of reformatting further comprising the step of: changing said AIS DS-3 to an IDLE DS-3 signal.
11. The method according to claim 1, wherein said fault location identifier comprises a formatted signal of the Synchronous Optical Network (SONET) having a structure with a supplementary byte, said method further comprising the steps of: using said supplementary byte to store an indication; derive the identification of said failure from said indication stored in said supplementary byte.
12. The method according to claim 10 characterized in that said bypass step further comprises the step of: using the byte Z4 in a path overload (POH) of said SONET signal to derive the message channel to transmit said fault signal The method according to claim 10, characterized in that said fault location identifier comprises a formatted Digital Leve
13. l 3 Service (DS-3) signal having a supplementary bit, said method further comprising the steps of: using said bit supplementary to store an indication; derive the identification of said failure from said indication stored in said supplementary bit. The method according to claim 12 characterized in that said derivation step further comprises the step of: using an X bit in said supplemental DS-3 bit to derive the message channel for the transmission of said fault signal.
14. 14. A method of identifying on all nodes of a communications path of a telecommunications network the location of a fault along said path when said failure occurs in said path, said network having a plurality of interconnected nodes by means of a plurality of circuits, said path including a number of said nodes interconnected by means of a number of said circuits, said method comprises the step of: making each node of said path: (i) monitor each incoming signal from nodes upstream of it along said trajectory; (ii) determine if each said incoming signal is an alarm signal indicating said failure; (iii) transmit an identifier to the nodes downstream thereof along said path until the detection of said alarm signal, said identifier indicating whether said failure has occurred immediately upstream thereof; (iv) continue transmitting said identifier a predetermined number of times until another identifier is received from a node upstream thereof or a normal signal through each node; (v) interrupt the transmission of said identifier until it receives either said other identifier or said normal signal; and (vi) conclude whether said failure has occurred immediately upstream of said node, if said identifier is transmitted said predetermined number of times.
15. The method according to claim 14 characterized in that it further comprises the step of: causing said node to conclude said failure that has occurred immediately upstream of the node sending said other identifier, if each said node has received said other identifier said number of predetermined times.
16. The method according to claim 14 characterized in that it further comprises the step of: concluding that said failure is not a real fault if said normal signal is received before said identifier has been transmitted or that said other identifier has been received said number of predetermined times.
17. The method according to claim 14 characterized in that it further comprises the step of: providing said identifier with an instruction to identify each said node as being one of the nodes adjacent to said failure along said communications path.
18. 18. The method according to claim 14, characterized in that it further comprises the step of: providing said identifier with an instruction to identify each said node and its respective node, which joins said failure along said communications circuit, respectively.
19. 19. The method according to claim 14, characterized in that said step to be performed comprises the step of: reformatting said alarm signal into a fault signal to transport said identifier to the nodes downstream of said node to inform said nodes downstream of the location of said failure.
20. 20. A method for identifying in all the nodes of a communication path of a telecommunications network the location of the mis-operation of the interval along said path, said network having a plurality of interconnected nodes by means of a plurality of intervals, said path including a number of said interconnected nodes by means of a number of said intervals, said method comprises the steps of: (a) causing each node on either side of said malfunction interval of said path: (i) to review each incoming signal from nodes upstream thereof along said path; (ii) determine if each said incoming signal is an alarm signal indicating a fault; (iii) transmit an identifier to the nodes downstream thereof along said trajectory until the detection of said alarm signal, said identifier indicating whether said failure has occurred immediately upstream thereof towards said malfunction interval; (iv) continue transmitting said identifier a predetermined number of times as long as no other identifier is received from a node upstream thereof or a normal signal by means of said each node; (v) interrupt the transmission of said identifier until it receives either said other identifier or said normal signal; (b) in each of the two adjacent nodes joining said malfunction interval, deciding whether said each adjacent node is one of the nodes joining said malfunction interval if each said adjacent node has transmitted its identifier said number of times predetermined; c) recover the location of said two adjacent nodes to thereby determine the location of said malfunction interval.
21. 21. The method according to claim 20 characterized in that, further comprises the step of: concluding that said interval is not malfunctioning if said normal signal is received before any of said adjacent said nodes has transmitted its identifier said predetermined number of times.
22. 22. The method according to claim 20, characterized in that it further comprises the step of: providing said respective identifiers of said adjacent nodes with the corresponding instruction to identify that each said adjacent node is one of the nodes joining said malfunction interval along the said communication path.
23. The method according to claim 20, characterized in that said step of carrying out further comprises the step of: reformatting said alarm signal towards a fault signal to transport said identifier to the nodes downstream of said node to inform said nodes down the location of said malfunction interval.
24. The method according to claim 23 characterized in that said alarm signal is an Alarm Indication Signal (AIS) of Synchronous Level 1 Transport Signal (STS-1), said reformatting step further comprises the step of: confirming said AIS in a Signal of Incoming Signal Failure (ISF).
25. 25. The method according to claim 23 characterized in that said alarm signal is a Level 3 Digital Service Alarm Indication (AIS) Signal (DS-3), said reformatting step further comprising the step of: changing said AIS of DS-3 to an IDLE signal of DS-3.
26. 26. The method according to claim 20, characterized in that said identifier comprises a formatted message of the Synchronous Optical Network (SONET) having a structure with a supplementary byte, said method also includes the steps of: using said supplementary byte to store an instruction; deriving the identification of said malfunction interval from said instruction stored in said supplementary byte.
27. The method according to claim 26 characterized in that said derivation step further comprises the step of: using a byte Z4 in a path overload (POH) of said SONET message to derive the message channel for the transmission of said identifier .
28. The method according to claim 20 characterized in that said identifier comprises a formatted signal of the Digital Service Level 3 (DS-3) having a supplementary bit, said method further comprising the steps of: using said supplementary bit to store an instruction; deriving the identification of said malfunction interval from said instruction stored in said supplementary bit.
29. 29. The method according to claim 28 characterized in that said derivation step further comprises the step of: using an X bit in said supplementary bit of the DS-3 to derive the message channel for the transmission of said identifier.
30. 30. The system for identifying in all nodes of a communication path of a telecommunications network the location of a fault along said path when said failure occurs in said path, said network having a plurality of nodes interconnected by a plurality of circuits, said trajectory including a number of said nodes interconnected by a number of said circuits, said system comprises: means of interconnection in each node of said trajectory to (i) monitor each incoming signal coming from nodes upstream of it along said path; (ii) determining whether each said incoming signal is an alarm signal indicating said failure; (iii) transmitting an identifier to the nodes downstream thereof along said path until the detection of said alarm signal, said identifier indicating whether said failure has occurred immediately upstream thereof; (iv) continuing the transmission of said identifier a predetermined number of times as long as no other identifier is received from a node upstream thereof or a normal signal through each node; (v) interrupting the transmission of said identifier until it receives either said other identifier or said normal signal; and (vi) concluding that said failure has occurred immediately upstream of said node, if said identifier is transmitted in said predetermined number of times.
31. 31. The system according to claim 30 characterized in that said interconnection means further cause each said node to conclude that said failure has occurred immediately upstream of the node sending said other identifier, if each said node has received said other identifier said predetermined number of times
32. 32. The system according to claim 30, characterized in that it further comprises - the decision means to conclude that said failure is not an actual fault if said normal signal is received before said identifier has been transmitted or said other identifier has been received. said predetermined number of times.
33. 33. The system according to claim 30, characterized in that it also comprises; means for providing said identifier with an instruction to identify that each said node is one of the nodes adjacent to said failure along said communications path.
34. 34. The system according to claim 30, characterized in that it also comprises; means for providing said identifier with instruction to identify respectively each said node and its pertaining node that joins said fault along said communications path.
35. 35. The system according to claim 30 characterized in that said means of effect further comprises: means for reformatting said alarm signal in a fault signal to transport said identifier to the nodes downstream of each said node to inform said nodes downstream the location of said failure.
36. 36. The system for identifying in all the nodes of a communication path of a telecommunications network the location of the malfunction interval along said path, said network having a plurality of nodes interconnected by a number of said intervals, said system comprises: means at each node on each side of said malfunction interval of said trajectory to (i) monitor each incoming signal from nodes upstream thereof along said path; (ii) determining whether said incoming signal is an alarm signal indicating said failure; (iii) transmitting an identifier to the nodes downstream thereof along said path until the detection of said alarm signal, said identifier indicating whether said failure has occurred immediately upstream thereof towards said malfunctioning interval; (iv) continuing the transmission of said identifier a predetermined number of times as long as no other identifier is received from a node upstream thereof or a normal signal through each node; (v) interrupting the transmission of said identifier until it receives either said other identifier or said normal signal; means for deciding that each of the two adjacent nodes joining said malfunction interval is one of the nodes joining said malfunction interval, if each said adjacent node has transmitted its identifier said predetermined number of times; and means for recovering the location of said two adjacent nodes to thereby determine the location of the malfunction interval.
37. 37. The system according to claim 36 characterized in that it further comprises: means for deciding that said interval is not malfunctioning if said normal signal is received before any of said adjacent nodes have transmitted their identifier said predetermined number of times.
38. 38. The system according to claim 36 characterized in that it further comprises: means for providing said respective identifiers of said adjacent nodes with the corresponding instruction to identify that each said adjacent node is one of the nodes that join said malfunction interval along the said communication path.
39. 39. The system according to claim 38 characterized in that said means in each said node further comprises: means for reformatting said alarm signal in a fault signal to transport said identifier to the nodes downstream of each said node to inform said nodes downstream the location of said malfunction interval.
40. 40. The system according to claim 36 characterized in that said alarm signal is a Signal of Alarm Indication (AIS) of the Level 1 Synchronous Transport Signal (STS-1), - and wherein said means in each said node further convert said AIS into an Incoming Signal Fault (ISF) signal.
41. 41. The system according to claim 36 characterized in that said alarm signal is an Alarm Indication Signal (AIS) of the Digital Service Level 3 (DS-3); wherein said means in each said node further convert said AIS of DS-3 into an IDLE signal of DS-3.
42. 42. The system according to claim 36 characterized in that said identifier comprises a formatted message of the Synchronous Optical Network (SONET) having a structure with one supplementary bytes, said system further comprising: an instruction stored in dich additional byte; means for deriving the identification of said malfunction interval from said instruction stored in dich additional byte.
43. 43. The system according to claim 42 characterized in that said derivation means further utilize the byte Z4 in a path overload (POH) of said SONET message to derive the message channel for the transmission of said identifier.
44. 44. The system according to claim 36 characterized in that said identifier comprises a formatted signal of the Digital Service Level 3 (DS-3) having a supplementary bit, said system further comprising: an instruction stored in said supplementary bit; means for deriving the identification of said malfunction interval from said instruction stored in said supplementary bit.
45. 45. The system according to claim 44 characterized in that said derivation means further utilize a bit X in said supplementary bit of the DS-3 to derive the message channel for the transmission of said identifier.
46. 46. An apparatus in each node to identify the location of said fault in said circuit in a communication network having a plurality of nodes and a plurality of communication circuits interconnecting said nodes, each of said nodes along a circuit of communications having detected a fault signal caused by a failure in said communications circuit, comprising: means for periodically transmitting a fault location identifier originated by said node in said communications circuit; means for stopping the transmission of said originating fault identifier originated until another identifier or a normal signal is received from an upstream node; and means for confirming whether said fault location identifier is representative of the correct location of said failure if said originating identifier was sent at least a predetermined number of times.
47. 47. The apparatus according to claim 46 characterized in that it further comprises means for detecting any incoming fault location identifier; means for confirming that any of said detected fault location identifiers is representative of the correct location of said failure when the same identifier is received said predetermined number of times and a normal signal is not received before the last of said predetermined number of times .
48. 48. The apparatus according to claim 46 characterized in that it further comprises means for determining that there is no fault in said communication circuit if a normal signal is received before said originated fault location identifier has been sent said predetermined number of times .
49. 49. The apparatus according to claim 46, characterized in that it further comprises an instruction that identifies one of the nodes joining said failure along said communications circuit that is provided in said fault location identifier.
50. 50. The apparatus according to claim 46 characterized in that it further comprises instructions that respectively identify both of the nodes joining said failure along said communication circuit that is provided in said fault location identifier.
51. 51. The apparatus according to claim 46 characterized in that, said apparatus further comprises: means for reformating said fault signal to another fault signal in such a way that the nodes downstream of said node are informed of said failure when said other fault signal is diffused therein after each said node has detected said failure signal. SUMMARY All nodes (12-24) in a malfunction communication circuit (42A) of a communication network are enabled to identify the fault location (92) that causes the malfunction of the circuit. Once the abnormality of the incoming signal in the circuit (402) is detected, each node (12-24) in the circuit first assumes that the fault is in the segment (42) of the circuit immediately upstream thereof, and in accordance with the above sends an identifier (410) from that fault location to its downstream nodes (18-24). Each node (12-24) periodically repeats the sending of its identifier (410) to its nodes downstream (18-24). A node (12-24) that has sent its identifier at least a predetermined number of times without receiving a similar identifier from another node upstream of it (406) or without having detected a normal signal during all that time, is determined to have to send an identifier that correctly identifies the failure in the communications circuit (414). If on the other hand, a node (18-24) receives a failure location identifier from a node (12-16) upstream thereof before it has completed sending its identifier a predetermined number of times (418), then that node would stop sending its own identifier downstream. And upon receiving the same fault location identifier from an upstream node (12-18) a predetermined number of times, that node would further recognize that the received identifier represents the correct failure location (420).