METHOD AND SYSTEM FOR DETECTING AN ISOLATED NODE IN A COMMUNICATIONS NETWORK

Abstract: A method and system for detecting an isolated node in a communications network. An isolated node condition occurs if all of the communications links to a node become unavailable thereby preventing all messages from leaving or entering the node. If this situation is not quickly rectified, the end office, and quite possibly the entire network, may fail. With such a method and system, a system administrator can immediately be notified of an isolated node and take the proper steps for correcting this situation.

Description: METHOD AND SYSTEM FOR DETECTING AN ISOLATED NODE IN A COMMUNICATIONS NETWORK TECHNICAL FIELD The present invention relates to calls and transactions in a communications network, such as an Signaling System Seven (SS7) network, and, more particularly, to monitoring transactions in an SS7 network to detect when an isolated node condition exists. BACKGROUND Common channel signaling networks, such as the Signaling System Seven (SS7) based signaling system, use dedicated channels to pass digital messages between system nodes for call setup, call control, call routing, and other functions. These dedicated signaling channels are part of a network that is separate from the network that carries the actual voice and data signals. An SS7 network is a separate switching system that is used prior to, during, and at the end of an actual voice or data call. The SS7 network is used to route control information. Whenever two switches or elements have to pass call control information during, prior to or at the end of a telephone call, they pass this data via the SS7 signaling network. There are three basic types of network node elements in a SS7 network. One of them is the Service Switching Point (SSP), which may be a central office switch, a tandem switch or an end office switch. A second principal node element is the Service Control Point (SCP). An SCP acts as a database query server for the rest of the network. An SCP is used in such applications as translating ported telephone numbers, routing 800 calls, tracking roamers in a cellular network, and Alternate Billing Service/Line Identification Database services (or ABS/LIDB) which provide operator-type services. The third principal node element is the Signal Transfer point (STP). An STP is essentially a packet switch that routes the messages among SSPs and SCPs. It is possible to combine these three different types of nodes into a single node. However, in North America, they are typically not combined. Usually, an SSP performs only switch functions, an SCP performs only control functions, and an STP performs only signal transfer functions. In European telecommunications systems, all of these different functions may be combined into one node. The SS7 network carries a great deal of information and is extremely critical to the operation of the telephone system. If an SS7 network is not functioning, or if portions of it are not operating, the telephone system simply cannot deliver calls, even though all of the voice circuits are operating properly. The capacity and complexity of the SS7 network is small in terms of the circuitry and bandwidth that are utilized by an end user compared to previous voice and data networks. The circuitry of the SS7 network is therefore much more critical. The actual elements in the SS7 network do not provide all of the information required in network operations to manage and to determine the health and state of an SS7 network. The topology of the network is such that STPs are typically deployed in a mated pair configuration at geographically separate locations. Connected to a mated pair of STPs are a set of SSPs and SCPs. This conglomeration of SSPs, SCPs and mated pair STPs is called a cluster. Clusters are then connected by links, such as D-Quad links, between STP mated pairs. When any transaction or message is sent between two different devices on the network, it is often the case that messages traveling from switch A to switch B travel one route on the network while the messages traveling from switch B to switch A travel on a different route. Network surveillance equipment can be used to monitor the links in an SS7 network. Such surveillance and monitoring equipment is disclosed in U.S. Patent No. 5,592,530, entitled TELEPHONE SWITCH DUAL MONITORS, and in pending applications serial numbers 09/092,428, entitled SYSTEM AND METHOD FOR DETECTING HIGH MESSAGE TRAFFIC LEVELS IN A COMMUNICATIONS NETWORK; 09/092,699, entitled SYSTEM AND METHOD FOR SIGNAL UNIT DATA STORAGE AND POST CAPTURE CALL TRACE IN A COMMUNICATIONS NETWORK; 09/092,256, entitled SYSTEM AND METHOD FOR GENERATING QUALITY OF SERVICE STATISTICS FOR AN INTERNATIONAL COMMUNICATIONS NETWORK; and 09/092,771, entitled SYSTEM AND METHOD FOR CORRELATING TRANSACTION MESSAGES IN A COMMUNICATIONS NETWORK, each filed June 6, 1998 and hereby incorporated by reference herein. The disclosed monitoring units are designed to capture and correlate as much signaling information as possible regardless the level of network activity. Because the messages may take different data paths it is difficult to perform this correlation above the transport layer when monitoring links at the STP sites. Network monitoring and message correlation can be used to troubleshoot and identify application level problems in the network. For example, if a subscriber has a problem getting his or her calls delivered, then the telephone company may attempt to fix the problem by doing a trace of all data pertaining to that subscriber's phone number. However, all of the data may not be located at one point in the network. The required data may be split in some fashion, wherein part of the information is in one STP and part is in the other STP of a mated pair. The two STPs in the mated pair may be in different cities separated by many miles. In an SS7 network, each telephone is connected to a single end office, which may be an SSP or some other switch. The end office is connected to the SS7 network through one or more STPs. All calls that are directed to a particular destination telephone must pass from an STP to that telephone's assigned end office via one or more communications links. If one of the communications links becomes unavailable, for example, due to a hardware problem, software problem, network outage, link failure, linkset failure or the like, and another communications link is connected to the end office, the STP will route the messages intended for the telephone via the other communications link. In certain situations, however, all of the communications links associated with a particular end office may become unavailable thereby preventing messages from entering or leaving the end office. As a result the end office, or node, is isolated from the rest of the network. If this situation is not quickly rectified, the end office, and quite possibly the entire network, may fail. Therefore, there is a need for a method and system for detecting such an isolated node in a communications network. With such a method and system, a system administrator can immediately be notified of an isolated node and take the proper steps for diffusing this volatile situation. SUMMARY OF THE INVENTION These and other objects, features and technical advantages are achieved by a method and system for detecting an isolated node, such as a Service Switching Point, in a communications network. The communications network includes communications links, such as A-links, that are coupled from the SSP to at least one other node, such as a Signal Transfer Point (STP), an Intelligent Peripheral (IP) or an end office. The communications network further includes monitoring units coupled to the communications links and components, such as a computer, a server and a database, coupled to the monitoring units. Monitoring units that continually monitor, in real time, all calls on a signaling network are disclosed in U.S. Patent No. 5,592,530, entitled TELEPHONE SWITCH DUAL MONITORS; and in application serial number 09/057,940, filed April 4, 1998, entitled SYSTEM AND METHOD FOR MONITORING PERFORMANCE STATISTICS IN A COMMUNICATIONS NETWORK, the disclosure of which is hereby incorporated by reference herein. The monitoring units monitor the communication links to which they are coupled. If a link becomes unavailable, the monitoring unit for that link generates an alarm indicating that event. The alarm may be sent to an associated component, such as a computer. If all of the communications links for a particular node become unavailable, then the monitoring unit would detect this condition when it correlates the alarms. The monitoring unit would then send another alarm to the computer or component indicating a node isolation. If one of the links to or from the node becomes available again, then the monitoring unit will clear the node isolation alarm. The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the feature will be described hereinafter which form the subject if the claims of the invention. It should be apparent by those of average skill in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention and that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. BRIEF DESCRIPTION OF THE DRAWING For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which: FIGURE 1 depicts a high level block diagram of a network monitoring system coupled to a communication network in an exemplary embodiment of the present invention; FIGURE 2 depicts a high level block diagram of an unavailable link in the communications network; FIGURE 3 depicts a high level block diagram of a node isolation in the communications network; FIGURE 4 depicts a high level block diagram of a network monitoring system coupled to a communications network in another embodiment of the invention; FIGURE 5 depicts a high level block diagram of a computer of the present invention; and FIGURE 6 depicts a flow chart of a method for detecting an isolated node in a communication network of the present invention DETAILED DESCRIPTION FIGURE 1 illustrates communications network 10, which may be a Signaling System Seven (SS7) network. Telephones 101 and 102 are coupled to end offices 103 and 104 via telephone lines 105 and 106. End offices 103 and 104, which may be Signaling Points (SPs) or Service Switching Points (SSPs), are coupled to STPs 107-110 via trunks 111 and 112, which are known as A-links in an SS7 system. Typically, STPs 107-110 are arranged in a mated pair configuration wherein C-Links, such as trunks 113 and 114, and link mated pairs 107 and 109 or 108 and 110 respectively. The mated pairs are linked via B-links, such as trunks 115 and 116. Other components may also be coupled to network 10, such as a Service Node (SN), an Intelligent peripheral (IP) or a Service Control point (SCP). SCP 117 is coupled to STPs 107 and 109 via links 118 and 119. SCP 117 may be used in network 10 to provide database services for applications such as 800, CLASS, and Local Number Portability (LNP). Calls and transactions between end offices 103 and 104 are routed via STPs 107-110 via links 111-116. Signaling units traveling between end office 103 and 104 may take any number of paths through network 10. Typically, signaling units traveling in one direction from end office 103 to 104 will follow the same path for one transaction or call. However, signaling units traveling in the opposite direction from end office 104 to 103 may take a different path for the same transaction or call. For example, if a user at telephone 101 initiates a call to a user at telephone 102, a Transaction Capabilities Application Part (TCAP) BEGIN message may be routed from end office 103 to end office 104 via STPs 107 and 108 across links I l ia, 115, and 112a. In response, a TCAP response message, such as a CONTINUE or an END message, may be routed from end office 104 to end office 103 via STPs 110 and 109 across links 112b, 116, and 11 lb. Generally, successive messages corresponding to the same transaction will travel from end office 103 to end office 104 through STPs 107 and 108, while messages traveling in the opposite direction will pass through STPs 109 and 110. In certain circumstances, such as for an 800 number call or for a call to an exchange or number that has been ported to a different switch, messages may be sent to SCP 117 to perform various database look-up functions. Signals or messages are exchanged with SCP 117 via links 118 and 119. In the present invention, network monitors (or monitoring units) 121-124 capture substantially all of the signaling units traveling through network 10. Each monitor, 121-124, is non-intrusively coupled, via connections 125-128, to all links associated with a particular STP 107-110. For example, monitor 124 is associated with STP 110 and captures all messages traveling across links 112a, 112b, 114 and 116. Similarly, monitors 121-123 monitor the messages passing through STPs 107-109 via links 125-127. Although two monitors may simultaneously monitor the signaling units and messages on a single link, no monitor is coupled to all of the links in network 10. For example, monitors 121 and 122 both detect messages on link 115. However, the other monitors, 123 and 124, are not coupled to link 115 and, therefore, will not detect any of the messages on link 115. The monitors 121 to 124 are coupled to each other via inter-monitor communication bus 129. The bus 129 may be part of a data network, such as a Wide Area Network (WAN). The monitors 121-124 may also be linked to a central server 130 or user workstations 131, as disclosed in pending application serial numbers 09/093,824, entitled TRANSACTION CONTROL APPLICATION PART (TCAP) CALL DETAIL RECORD GENERATION IN A COMMUNICATION NETWORK; and 09/094,122, entitled SIGNALING UNIT DATA STORE/AUTOMATIC MAINTENANCE MESSAGE STORAGE IN A COMMUNICATIONS NETWORK, the disclosures of which are hereby incorporated by reference herein. Once a call or transaction record is complete, the record is then sent to server 130 for further processing. Monitors may determine that a record is complete when an end message is detected for that particular call or transaction. Workstation 131 provides network service providers or other users with access to retrieve data or to configure server 130 or monitors 107-110. FIGURE 2 illustrates communications network 10 in which communication link 112b has become unavailable. Monitor 124, which is monitoring link 112b, notes that link 112b is now unavailable and sends a link unavailable alarm or a linkset unavailable alarm to server 130. Server 130 may format the alarms into a format selected by a user or customer and forward these alarms to workstation 131 or to an external system 132. The alarms may then be displayed in real time or placed in a database for future display. Alarms may be displayed on the workstation 131 or on the external system 132, which may be a server or workstation. The external system 123 can also receive the alarm directly from a monitor, such as from monitor 123 as shown. Additionally, workstation 131 may receive the alarm from a monitor, such as from monitor 124. Although link 112b to end office or node 104 is unavailable, calls can still be made and received by node 104 via link 112a. As used herein, the term node is used to refer to network elements such as an STP (such as STP 107), an SCP (such as SCP 117), an SP (such as SP 104), an SSP (not shown), an Intelligent Peripheral (IP)(not shown), a Service Node (SN)(not shown), an end office (such as end office 103) or the like. FIGURE 3 illustrates the communications network 10 in which communications link 112a (in addition to link 112b) becomes unavailable. When link 112a becomes unavailable, monitor 124, which is monitoring link 112a, notes that the link 112a is now unavailable and sends a link unavailable alarm to the server as described above. Since all of the links to and from the node 104 are unavailable, no calls can be made to or received from the node 104. Therefore, switch 104 is an isolated node. Monitoring unit 124 correlates the link unavailable alarms associated with links 112 a and 112b and, since all of the links to and from the node 104 are unavailable, sends a node isolation alarm to server 130, workstation 131, and/or external system 132 as described above. When a link unavailable alarm or a node isolation alarm is displayed on the server 130, workstation 131, and/or external system 132, a user or operator receives this information and may immediately take action to diffuse a potentially serious situation. The alarms are received by the user or operator via a graphical user interface (GUI) on any of the components. A pictorial view of the communications network may be visible and if a link becomes unavailable, the color of the link or any other unavailable component on the GUI may change colors, for example, from green to red. In addition, a textual representation of the link unavailable alarm may appear on one of the components. If the operator is able to provide a solution and make at least one of the unavailable links (112a or 122b) become available, then monitoring unit 124 would send a message to server 130, workstation 131 or system 131 indicating that node 104 is available. At this point, the node 104 is no longer isolated and is able to receive and transmit messages via the available link(s). Additionally, the color of the link on the GUI may change from red back to green. FIGURE 4, which is similar to FIGURE 1, illustrates the communications network 10 in which monitoring unit 110 monitors link 112b and monitoring unit 108 monitors link 112a. In this scenario, two different monitors are monitoring two different links that are connected to end office 104. If link 112b becomes unavailable, signaling unit 110 would send a link unavailable alarm to server 130. Similarly, if link 112a becomes unavailable, signaling unit 108 would send a link unavailable alarm to server 130. Server 130 would then correlate the alarms and would initiate a node isolation alarm. FIGURE 5 illustrates another embodiment of the present invention that includes a computer 501, which comprises processor 502 and memory 503. Memory 503, which is coupled to processor 502, includes operating instructions that, when read by the processor, cause the processor to monitor communication links in a communications network. If one of the communication links becomes unavailable, an alarm is sent by processor 502. If all of the communication links become unavailable, processor 502 correlates the alarms and sends a node isolation alarm. The operating instructions further cause the processor to send a message indicating an available node if at least one of the communication links becomes available. FIGURE 6 is a flowchart 600 illustrating an exemplary method for detecting an isolated node in a communication network. In step 601, a monitoring unit monitors all of the communications links to a node. At step 602, if one of the communications links becomes unavailable, the monitoring unit sends a link unavailable alarm to a component, such as server 130 or workstation 131. At step 603, if all of the communications links become unavailable, the monitoring unit correlates the link unavailable alarms, and in step 604 the monitoring unit sends a node isolation alarm to the component. At step 605, if at least one of the communication links becomes unavailable, the monitoring unit sends a message indicating an available node. It will be understood that the names of the various alarms may be changed and that the alarms may be concurrently or independently displayed on any device. Furthermore, the monitoring units may also be configured to detect and warn of a network or cluster isolation in which a group of nodes would become unavailable. Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.

Claims: WHAT IS CLAIMED IS: 1. A method for detecting an isolated node in a communications network, wherein the communications network includes communication links coupled to nodes, a monitoring unit coupled to the communication links, and a component coupled to the monitoring unit, the method comprising the steps of: monitoring communication links coupled to a node; if one of the communication links becomes unavailable, sending a link unavailable alarm to the component from the monitoring unit; and if all of the communication links become unavailable, correlating all related link unavailable alarms by the monitoring unit, and sending a node isolation alarm to the component from the monitoring unit. 2. The method of claim 1 further comprising the step of: if at least one of the communication links becomes available, sending an available node message from the monitoring unit to the component. 3. The method of claim 1, wherein the component comprises at least one element selected from the group consisting of: a computer, a server, and a database. 4. The method of claim 1 , wherein the communications network includes a plurality of monitoring units and a plurality of components, wherein the plurality of monitoring units are coupled to each other. 5. The method of claim 1, wherein said nodes are selected from the group consisting of: a Signal Transfer Point (STP); a Signal Control Point (SCP); a Switching Point (SP); a Service Switching Point (SSP); an Intelligent Peripheral (IP); a Service Node (SN); and an end office. 6. A system for detecting an isolated node in a communications network, wherein the communications network includes communication links coupled to nodes, a monitoring unit coupled to the communication links, and a component coupled to the monitoring unit, the system comprises: means for monitoring all of the communication links to a node; means for sending a link unavailable alarm to the component if one of the communication links becomes unavailable; means for correlating the link unavailable alarms by the monitoring unit if all of the communication links become unavailable; and means for sending a node isolation alarm to the component. 7. The system of claim 6 further comprises: if at least one of the communication links becomes available, means for sending a message indicating an available node to the component. 8. The system of claim 6, wherein the component is selected from the group consisting of: a computer, a server, and a database. 9. The system of claim 6, wherein the communications network includes a plurality of monitoring units and a plurality of components, wherein the plurality of monitoring units are coupled to each other. 10. The system of claim 6, wherein the nodes are selected from the group consisting of: a Signal Transfer Point (STP); a Signal Control Point (SCP); a Switching Point (SP); a Service Switching Point (SSP); an Intelligent Peripheral (IP); a Service Node (SN); and an end office. 11. A computer comprising a processor and memory coupled to the processor, wherein the memory includes operating instructions that, when read by the processor, cause the processor to: monitor communication links in a communications network; send an alarm if one of the communication links becomes unavailable; and if all of the communication links become unavailable, correlate the alarms, and send a node isolation alarm. 12. The computer of claim 11 wherein, if at least one of the communication links becomes available, the operating instructions further cause the processor to send a message indicating an available node. 13. The computer of claim 11 , wherein the node is selected from the group consisting of: a Signal Transfer Point (STP); a Signal Control Point (SCP); a Switching Point (SP); a Service Switching Point (SSP); an Intelligent Peripheral (IP); a Service Node (SN); and an end office.

Inventors: BROCKMAN PIERCE EDWARD, SHAMLIAN FRANK BRUCE, BROCKMAN, PIERCE, EDWARD, SHAMLIAN, FRANK, BRUCE
Applicants: INET TECHNOLOGIES INC, INET TECHNOLOGIES, INC.
Application year: 2000
Main classification: H04M3
IPC codes: H04M3, H04Q3