GB2353664A

GB2353664A - Telecommunications event reporting

Info

Publication number: GB2353664A
Application number: GB9919635A
Authority: GB
Inventors: Andrew George Lauder
Original assignee: Nokia Telecommunications Oy
Current assignee: Nokia Oyj
Priority date: 1999-08-20
Filing date: 1999-08-20
Publication date: 2001-02-28
Anticipated expiration: 2019-08-20
Also published as: GB2353664B; GB9919635D0

Abstract

Apparatus (10) for reporting events in, for example, a node (3) of a telecommunications system has a buffer memory (14) for storing event notifications generated in the node. The buffer memory (14) is interrogated at intervals, and the notifications yielded by a given interrogation are processed by compiling means (16). The compiling means (16) creates a single report of all those event notifications which has a common header, for transmission on the management network of the system. The system is better able to carry a single report of a large number of events than a large number of reports of individual events, and the apparatus reduces or avoids the risk of the management network being flooded by bursts of events.

Description

2353664 TITLE: EVENT REPORTING IN TELECOMMUNICATIONS SYSTEMS

Field of the Invention

This invention relates to apparatus for, and a method of, reporting events at one site in a telecommunications network to another site on the network. The invention also relates to a node for a telecommunications network, the node being equipped with such apparatus, and to an event report for transmission over the network.

Backqroufld to the Invention A modern digital telecommunications systems has many elements, such as nodes, which are remotely managed by an operations and maintenance station. The operations and maintenance station communicates with the elements over a management network. Various events at a given element therefore need to be reported over the management network to the operations and maintenance station. For example, any change in status of a node, f or example the triggering or clearing of an alarm or protection switch, is treated as an event.

However, certain occurrences, f or example a break in a cable connecting the node to another part of the network can give rise to a burst of a large number of events. If the node has a conventional event forwarding discriminator (such as that described in ITU-T Standard X.721) a large number of event reports are sent over the management network as a result. This can lead to a "network flooding" situation in which the volume of event reports being transported across the network interferes with the normal management of the network. In addition, bursts of event reports can cause processing problems in both the network elements that generated them and the management system that receives them.

2 It is known to reduce the number of bursts of event reports by providing a filtering function in the event forwarding discriminator. This function is used to filter out those types of notification that can arrive in bursts. For example, in an SDH network, a high order failure can cause a burst of lower order switching notifications which can therefore be filtered out.

To that end the node may have an alarm masking mechanism. This ensures that, when a failure occurs, any alarms that are a consequence of this failure inside the node are not reported. There may also be other alarms that are not masked by the masking mechanism, but which nevertheless are not normally reported.- Thus, the discriminator prevents bursts of event reports simply by not reporting at least some of those types of event which may occur in bursts. However, as a result, the management system no longer receives event reports about certain classes of event and so needs to obtain this information in some other way (for example by polling the elements of the network).

Alternatively, bursts of events can be prevented from causing corresponding bursts of event reports by appropriately configuring the managed software and/or hardware objects in the network element. Those managed objects that can raise notifications of events that may occur in bursts implement a managerially configurable switch that allows those notifications to be suppressed. The management system then has the option of enabling or disabling the generation of those notifications (and therefore of the corresponding event reports) on a object by object basis.

If the management system only enables generation of notifications for those objects that are considered to be important, then any event report burst can be limited to a size that the network and management system can handle.

3 This approach suffers from the problem that only some of the managed objects are monitored through the event reporting system. The remaining objects need to be monitored by some other means. It is also quite possible for the management system to enable notifications from too many managed objects so that network flooding still occurs.

SummarV of the Invention According to a first aspect of the invention, there is provided apparatus for creating reports of events, detected in an element at a site on a telecommunications system, for transmission to another site on the system, the apparatus comprising means for receiving notifications of said events from the element; a buffer memory for storing said notifications; interrogation means for interrogating the memory at intervals and compiling means for receiving notifications from the buffer memory when the latter is interrogated and creating a scheduled event report in which the notifications are concatenated, wherein, in use, data on a plurality of notifications, which are stored in the buffer memory in the interval between successive interrogations, are contained in a single report.

Preferably, the apparatus is so arranged that all the notifications stored in the memory in any given interval between successive interrogations are included in a single report.

The apparatus therefore handles a burst of notifications in an element by incorporating them into a smaller number of scheduled event reports, each of which carries more data than a report of a single event. In practice a burst of notifications may be incorporated into one or two reports, depending on whether the burst occurs during just one scheduling period or covers a period of time that includes an interrogation of the buffer memory.

4 In general, management networks of telecommunications systems can handle the transport and routing of a large message much more efficiently than multiple small messages. Consequently, a burst of events which, if reported individually, would flood the network, are reported in a smaller number (possibly just one) of reports which can be accommodated by the network.

Preferably, the compiling means is so arranged that each report created thereby has a common header for all the notification data in the report.

Typically, the header for a data packet to be transmitted over a telecommunications system precedes the packet and identifies the datapacket, its source and intended destination, and includes a time stamp and information for a facilitating error checking of the packet.

Where the header is used for a number of data packets containing information on a number of notifications, further information on the contents of the data packets might be needed (compared with a header for an individual packet). However, the common header avoids the unnecessary repetition of header data, for example source and destination data, which would occur in apparatus which reports notifications individually. This advantage outweighs any additional processing demands arising from the increased size of the common header compared with a header for an individual data packet.

Preferably, the interrogation means includes override means for monitoring the number of notifications stored in the buffer, and causing the compiling means to create said report if the number exceeds a given threshold.

Said threshold may correspond to the maximum capacity of the buffer memory means or the maximum size of data packet that can be transmitted over the management network of the telecommunications system.

Thus, the interval between successive interrogations of the buffer memory means is reduced if the rate at which event notifications are supplied to the memory means is so high that, with a normal interval between interrogations, the memory would fail to store all the notifications or the subsequent event report would be too large to be handled by the network, depending on which factor determines the threshold.

Preferably, the apparatus includes means for transmitting a heartbeat signal over the management network to confirm that the apparatus is functional if no event notifications are obtained from the buffer memory by one or more interrogations.

Said heattbeat signal is preferably sent if a plurality of successive interrogations yield no event notifications.

Thus, even if there are no event notifications to report, the apparatus will transmit signals which have the effect of confirming that no notifications have been received and that the apparatus is functioning. This removes the need for the management system to poll network elements (equipped with said apparatus) to check that they are operating properly.

Preferably, the apparatus includes counter means for counting the number of times the buffer memory is interrogated, said counter means being arranged to be reset whenever an interrogation of the buffer memory results in the transmission of an event report, and to trigger the sending of said heartbeat signal if a number of interrogations registered on the counter means exceeds a given threshold.

According to a second aspect of the invention, there is provided a node for a telecommunications system, the node having apparatus in accordance with the first aspect of the invention, wherein the node comprises a number of managed hardware and software objects which include the facility for generating event notifications which are supplied to the buffer 6 memory of the apparatus, the apparatus being operable to incorporate said notifications into event reports for transmission to the management system of a network of which the node forms a part.

The invention also lies in a method of reporting events in one or more elements of a telecommunications system to a site at another location on the system, the elements being operable to generate notifications of said events, the method comprising concatenating a plurality of said notifications into a single report and transmitting the report over the system to said site.

The invehtion also lies in an event report from a managed element of a telecommunications system, the report containing data on a plurality of events, and a common header for said data, the report also being in a form in which it can be transmitted over the management network of the telecommunications system.

Brief Description of the Drawings

The invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 is a simplified schematic block diagram of a telecommunications network; Figure 2 is a schematic block diagram of a node of the system fitted with apparatus in accordance with the invention; Figure 3 is a pictorial representation of an event report prepared by conventional means; and Figure 4 is a corresponding representation of a report prepared by the apparatus and method of the present invention.

7 Detailed Description

Figure 1 shows five nodes of a digital telecommunications system, referenced station 1 - station 5. The nodes are managed by a remote operations and maintenance centre 6 which communicates with the nodes 1-5 through management links as indicated by the solid connecting lines, for example the line 8.

In reality, the system would include a large number of other nodes, many of which would be connected to user terminals (for example telephones) and a large number of further signal links interconnecting the nodes. However, these features have been omitted from Figure 1 for the sake of clarity. The management links are provided by cabling that also carries payloads (ie data to be transmitted and received by subscribers to the system), the management signals being carried in the overhead to the payload.

Each of the nodes 1-5 is an SDH multiplexer which includes a large number of managed hardware/ software objects as described by various published documents from the ITU derived from the "systems management framework" outlined in the X.700 series of the International Standards laid down by the ITUT.

Again, for the sake of clarity, these objects have been omitted from the node 3 as shown in Figure 2.

Each of the nodes 1-5 has its own scheduled event reporting apparatus which is in accordance with the invention and which is identical to the scheduled event reporting apparatuses of the other nodes. Accordingly, only the scheduled event apparatus, generally referenced 10, of the node 3 will be described.

With reference to Figure 2, that apparatus comprises a buffer memory 12 which is linked to the managed objects of the node 8 3 in such a way as to receive event notifications from the managed objects. The buf f er memory has an input port and an output port, both of which are connected to an interrogation device 14 which has a further output connected to a compiling device 16.

In use, events in the managed objects of the node 3 cause those objects to submit event notifications to the buffer memory 12 as indicated by the arrows 18. The buffer memory 12 stores those notifications until it receives on its input port an interrogation signal from the device 14. The device 14 receives a signal from a clock source (not shown) which causes it to interrogate the buffer memory at regular intervals which are conf gured by the management system of the network. During each of those intervals, the buffer memory 12 also sends a signal to the interrogation means 14 each time a further event notification is loaded into the memory 12.

The chosen length of each interval provides a trade off between latency in the reporting of events and efficiency of transport in the management network. A large interval length will lead to many more events being gathered into a single concatenated report and so will make more efficient use of the network bandwidth. However this mechanism can delay the reporting of an event for up to the polling period and so a large interval length will introduce longer potential latency. The time chosen will depend on the size of the network, the capacity of the management network and the latency that is acceptable to the operator. Typically the interval can be in the region of 1 to 10 seconds, but values outside this range may be required in some situations.

The operator may also wish to set different periods in different nodes. For example, high latency may be acceptable for a remote node that is not carrying important traffic, while low latency may be desirable for a key node in a central location.

9 Each time this happens, a count as registered on a counter/ comparator 20 connected to the interrogation device 14 is incremented by one count. If the count registered on the counter/ comparator 20 exceeds a given threshold, corresponding to the maximum size of report that can be transmitted over the management network, the interrogation means 14 is triggered to send. an interrogation signal to the buffer memory 12 before the end of the normal interval. If this happens, the counter/ comparator 20 is reset to zero and the next normal interval runs from the time at which the interrogation signal was generated. If the threshold is not reached within the normal interval, the counter/ comparator 20 is reset.

In response to each interrogation signal, the memory 12 transmits its stored data to the interrogation device 14, and then clears itself so that each event notification stored in the memory is sent to the interrogation device 14 only once.

The data on notifications received by the device 14 are, in turn, relayed to the compiling device 16 which generates a scheduled event report, an example of which is shown in Figure 4.

The scheduled event report has a header which sets out the destination of the report, (ie the centre 6), the source of the report (the node 3), and includes error checking and time stamp data. The header also includes packet identification for enabling the centre 6 to send an acknowledgement of the receipt of the report to the node 3. This header data is identical to the header data included in a conventional report of the type shown in Figure 3, in which the header, referenced 22 is conveyed with data 24 on time of occurrence and nature of a single event. However, as is shown in Figure 4, the header 26 is used to convey a number of data blocks (four in this example) 28, 30, 32 and 34, each of which sets out the time of occurrence and nature of a respective event. The header 26 therefore includes additional information on the number of events being reported.

Although the header 26 contains more information than the header 22, it avoids the needless repetition of information, for example on the destination and source of the report, which would occur if each of the data blocks 28, 30, 32 and 34 were to be transmitted with its own respective header.

The interrogation device 14 is also connected to a second counter and comparator 36 which is incremented by 1 every time the buffer memory 12 is interrogated when it is empty, and hence when it yields no data on event notifications. When the number registered in the counter and comparator 36 passes a predeterTined threshold, for example 5 or 10, the counter/ comparator 36 resets itself and sends a signal to the compiling means 16, causing the latter to transmit a heartbeat signal to the management station of the telecommunications system. This tells the system that the node is still running and that there is a communications path to the node, and thus removes the need for the management system to poll the nodes to check that they are operating properly.

The threshold applied by the counter 36 can be programmable so that the counter 36 can be configured for a specific network.

The value of the threshold is chosen to provide a trade of f between the amount of traf f ic that is generated by these heartbeat messages and the maximum time taken to detect a f ailure in the management connection to a node. In general, it is expected that network problems are rare. Consequently, although large burst of events can occur, for most of the time there are very few events to report. Because of this the management network is generally "quiet". If the threshold (and hence the heartbeat interval) is set to too small a value, and if the network is large, then the management network can become full of heartbeat messages. This defeats the object of reducing loading of the management network.

11 Accordingly, the factors which may be considered in determining the threshold are: the number of nodes in the network (more nodes require a bigger number to keep the overall number of heartbeat notifications under control); the reliability of the management network (a high reliability network should not need such regular monitoring); the importance of the node (a node in a- key location may be given a smaller number, so that it generated heartbeats more frequently).

Thus, for example, higher thresholds of numbers registered in the counter and comparator 36 may be used where the management network is known to have good reliability.

It will be appreciated that there are a number of modifications and developments to the disclosed embodiment which may be made without departing from the scope of the invention. Thus, for example, the buffer may receive notifications from the managed objects via a standard event forwarding discriminator set up to allow the management system to control the types of report that it receives. The discriminator can receive and filter notifications in a conventional manner, the remaining notif icat Lons then being passed into the buf f er memory 12. In addition, any data compression scheme (for example "Zip") and/or optimised encoding can be used on the data of the scheduled event report to achieve a further reduction in the amount of data transferred over the management network. Compression algorithms generally achieve better compression ratios as file sizes increase, and so compression of a scheduled event report can be expected to be more effective than compression of multiple standard individual event reports.

12

Claims

1. Apparatus for creating reports of events, det ected in an element at a site on a telecommunications system, for transmission to another site on the system, the apparatus comprising means for receiving notifications of said events from the element; a buffer memory for storing said notifications; interrogation means for interrogating the memory at intervals and compiling means for receiving notifications from the buffer memory when the latter is interrogated and creating a scheduled event report in which the notifications are concatenated, wherein, in use, data on a plurality of notifications, which are stored in the buffer memory ifi the interval between successive interrogations are contained in a single report.

2. Apparatus according to claim 1, in which the apparatus is so arranged that all the notifications stored in the memory in any given interval between successive interrogations are included in a single report.

3. Apparatus according to claim 1 or claim 2, in which the compiling means is so arranged that each report created thereby has a common header for all the notification data in the report.

4. Apparatus according to any of the preceding claims, in which the interrogation means includes override means for monitoring the number of notifications stored in the buffer, and causing the compiling means to create said report if the number exceeds a given threshold.

5. Apparatus according to claim 4, in which said threshold corresponds to the maximum size of data packet that can be transmitted over the management network of the telecommunications system.

13 6. Apparatus according to any of the preceding claims, in which the apparatus includes means for transmitting a heartbeat signal over the management network to confirm that the apparatus is functional if no event notifications are obtained from the buffer memory by at least one interrogation.

7. Apparatus according to claim 6, in which said heartbeat signal is preferably sent if a plurality of successive interrogations yield no event notifications.

8. Apparatus according to claim 6 or claim 7, in which the apparatus includes counter means for counting the number of times the buffer memory is interrogated, said counter means being artanged to be reset whenever an interrogation of the buffer memory results in the transmission of an event report, and to trigger the sending of said heartbeat signal if a number of interrogations registered on the counter means exceeds a given threshold.

9. A node for a telecommunications system, the node having apparatus in accordance with any of the preceding claims, wherein the node comprises a number of managed hardware and software objects which include the facility for generating event notifications which are supplied to the buffer memory of the apparatus, the apparatus being operable to incorporate said notifications into event reports for transmission to the management system of a telecommunications network of which the node, when installed, forms a part.

10. A method of reporting events in one or more elements of a telecommunications system to a site at another location on the system, the elements being operable to generate notifications of said events, the method comprising concatenating a plurality of said notifications into a single report and transmitting the report over the system to said site.

14 11. An event report from a managed element of a telecommunications system, the report containing data on a plurality of events, and a common header for said data, the report also being in a form in which it can be transmitted over the management network of the telecommunications system.

12. Apparatus substantially as described herein with reference to, and as illustrated in, the accompanying drawings.

13. A telecommunications node substantially as described herein with reference to, and as illustrated in, the accompanying drawings.

14. A m-.-t-hod substantially as described herein with reference to the accompanying drawings.

is. An event report substantially as described herein with reference to, and as illustrated in Figure 4 of the accompanying drawings.