TECHNICAL FIELD OF THE INVENTION

The present invention relates to a system and method for managing and monitoring a network system using Simple Network Management Protocol (SNMP), and more particularly, the present invention relates to a system and method for tracking, detecting, and recovering lost SNMP traps in the network.

BACKGROUND OF THE INVENTION

Simple Network Management Protocol is a widely used application-layer protocol for managing and monitoring network elements. In the SNMP system, a managed device is capable of sending SNMP traps to alert an SNMP manager upon encountering a problem in the system. The SNMP trap is transmitted in communication mode with a user datagram protocol (UDP). However, no communication path is established in the UDP communication mode. Thus, the SNMP trap provides no confirmation that the trap is received by the manager, and the SNMP traps transmitted may be lost.

It is difficult for the network management system to make any confirmation on the event notification in the event that the SNMP trap that is transmitted from the managed devices is lost. The status of the managed devices will be shown incorrectly or the necessary actions that need to be taken on the managed devices are delayed.

United States Patent Publication No. 20040006619 A1 disclosed a trap structure for reporting an event to a network management system, wherein the trap includes management information for tracking individual trap messages. Lost trap message is detected and retransmission may be requested. In this disclosed patent publication, no additional information is embedded in the transmitted trap and retransmission is necessary when any lost trap is detected. United States Patent Publication No. 20060129674 A1 disclosed a network monitoring system for tracking transmission of SNMP traps. The system comprises a first transmitting unit for transmitting SNMP traps to a monitoring apparatus, and a second transmitting unit for transmitting second information to the monitoring apparatus by a different communication method, such as by email. This system is redundant in that the system requires two messages to be sent for every event that has occurred. In view of the above, it is advantageous to provide an SNMP trap monitoring system which is able to track any lost SNMP trap during the course of transmission from a network element to a managing station, and the information on the lost SNMP trap can be retrieved from the received SNMP trap so that retransmission may be avoided.

SUMMARY OF THE INVENTION

It is an objective of the present invention to provide a system and method for monitoring the transmission of SNMP trap between a network element and a network managing station.

It is also an objective of the present invention to provide a system and method for detecting lost SNMP traps by tracing the sequence number appended to every transmitted SNMP trap.

It is yet another objective of the present invention to provide a system and method for embedding information on the previously transmitted SNMP traps to the SNMP trap to be transmitted for allowing the managing station to take actions without retransmitting the lost SNMP trap.

The present invention relates to a system for monitoring transmission of SNMP traps from a network element to the network management station and recovering SNMP traps which are lost, said SNMP trap is created by the network element upon detecting an event affecting the network element. The system further comprises a trap transmission management module provided in the network element, for generating and maintaining a sequence number for the SNMP trap, appending an identifier of the previously transmitted SNMP traps. A trap transmission database is provided for storing the transmitted SNMP traps. A trap reception management module is provided in the network management station, for identifying any lost SNMP trap according to the sequence number of the SNMP trap received, extracting the identifier of the lost SNMP trap, determining whether re-transmission of the lost SNMP trap is required, and requesting lost SNMP trap retransmission from the network element. A trap reception database is provided for storing the received SNMP trap.

In one aspect of the invention, the object identifiers (OID) of the previously transmitted SNMP are compiled into a list of historical traps information for embedding into an SNMP trap to be transmitted.

The present invention also relates to a method for monitoring transmission of SNMP traps. The method comprises the steps of appending a sequence number and a list of identifiers of the previously transmitted traps to a current SNMP trap to be transmitted by the network element, storing the SNMP trap in a trap transmission database, transmitting the SNMP trap to the network management station, storing the SNMP trap in a trap reception database of the network management station, detecting any lost SNMP trap by comparing the sequence number of the current SNMP trap and the sequence number of the stored SNMP trap by the network management station, determining whether a trap retransmission request is required, generating and transmitting a trap retransmission request from the network management station to the network element, retrieving the lost SNMP trap from the trap transmission database based on the sequence number, and retransmitting the retrieved lost SNMP trap to the network management station. BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is further described hereinafter with reference to the embodiments shown in the accompanying drawings in which: Figure 1 is a block diagram showing a system for managing and monitoring SNMP traps transmission between a network element and a network managing station according to the present invention.

Figure 2 is a diagram showing a process for transmitting an SNMP trap by the network element according to the present invention.

Figure 3 is a diagram showing an overview process for receiving SNMP traps and detecting as well as recovering lost SNMP traps according to the present invention.

Figure 4 is a diagram showing a process for re-transmitting an SNMP trap by the network element according to the present invention.

Figure 5 is a diagram showing trap transmission flow between the network managing station and the network element in an exemplary scenario according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention and the preferred embodiments will now be described in with reference to the accompanying drawings. These embodiments as described, however, should not be construed to limit the scope of the present invention.

With reference to Figure 1 , the present invention relates to a system for monitoring transmission of SNMP traps from a network element (10) to the network management station (20). If an event affecting the network element (10) has occurred, an SNMP trap is generated and transmitted to the network management station (20) so that further actions can be taken by the network management station (20). In a preferred embodiment, the network element (10) comprises an SNMP agent (11) for performing SNMP operations including detection of the event affecting the network element (10) and generation and transmission of the SNMP traps to the network management station (20). A management information base (MIB) file is contained in the network element (10) for defining all SNMP traps with an identifier. The identifier used in SNMP traps is preferably an object identifier (OID). A trap transmission management module (12) is provided in the network element (10) for generating and maintaining the sequence number or timestamp for the SNMP trap. In a preferred embodiment, each of the SNMP generated is appended with a sequence number in a consecutive manner. The identifier of the previously transmitted SNMP traps is also appended to the SNMP traps. A trap transmission database (13) is connected to the trap transmission management module (12) for storing the transmitted SNMP traps and the information thereof.

The network management station (20) comprises an SNMP manager (21 ) for receiving the SNMP traps transmitted from the network element (10) and performing SNMP operations on the received SNMP traps. Similarly, the network management station (20) contains an MIB file for defining the SNMP traps with the object identifier. A trap reception management module (22) is connected to the SNMP manager (21) for identifying any lost SNMP trap according to the sequence number of the SNMP trap received, extracting the identifier of the lost SNMP trap, determining whether re-transmission of the lost SNMP trap is required, and requesting lost SNMP trap retransmission from the network element (10). The network management station (20) also comprises a trap reception database (23) for storing the received SNMP traps.

In a preferred embodiment, the MIB file in both the network element (10) and network management station (20) is a hierarchical database allocating the identifiers for the SNMP traps. Specifically, the identifier used is an object identifier (OID) which is represented in a specific integers format. An example of the OID is ".1.3.6.1.4.1.13643.180.1 " In a preferred embodiment, the number of identifiers of previously transmitted SNMP traps for appending to an SNMP trap is configurable. The list of previously transmitted SNMP traps is preferably known as historical trap information. The number of identifiers of previous SNMP traps to be appended to the SNMP trap is configurable depending on the user. An example of the historical traps information is shown in Table 1 below. If the currently transmitted SNMP trap is trap no. 4, and the number of identifiers predetermined for appending to the SNMP trap is 2, then the historical trap information would be the OIDs of SNMP traps no. 3, and 2, which are ".13643.180.1.1.3.2.9", ".13643. 80.1. 1.3.2.15".

Table 1 : An example of the historical traps information.

The present invention also relates to a method for monitoring transmission of SNMP traps from the network element (10) to the network management station (20) and recovering SNMP traps which are lost. With reference to Figure 2, an SNMP trap is generated when the network element (10) detects an event occurring in the system (101). The sequence number is generated and added to the SNMP traps generated (102). A predetermined number of identifiers such as OIDs are compiled into the list of the historical trap information, whereby the default number of OIDs is predetermined and is read by the system (103) before the compilation of OIDs commences. Then, the list of the OIDs is also appended to the SNMP trap (104). In a preferred embodiment, the list of identifiers of the previously transmitted SNMP traps is arranged in descending order. The SNMP trap is then transmitted (105) and the information of the transmitted SNMP trap is stored (106) in the trap transmission database (23).

The process of detecting and recovering the lost SNMP traps is shown in Figure 3. Once the network management station (20) receives an SNMP trap (201) from the network element (10), the SNMP trap is stored (202) in the trap reception database (23). The network management station (20) then detects any lost SNMP trap by comparing the sequence number of the current SNMP trap and the sequence number of the stored SNMP trap. Since the sequence number is issued in consecutive manner, any discontinuity in the received trap sequence number would be easily identified. The network management station (20) processes the received SNMP trap accordingly (203) if no lost SNMP trap is detected. Otherwise, the lost SNMP trap is identified (204) and the OID of the lost SNMP trap is extracted from the currently received SNMP trap according to the historical trap information appended to the SNMP trap. The extracted OID is stored in a list of the lost SNMP traps (205). Having the OID extracted, the system then determines whether more information is needed for the lost SNMP. If more information is required, the number of OIDs required in the list of lost SNMP traps is determined (206), and a retransmission request is sent (207) to the network element (10) for transmitting the lost SNMP traps from the trap transmission database (13). If the OID information is not sufficient, the trap reception database (10) is updated (208) and the lost SNMP trap is processed (209). The list of the lost SNMP traps is reduced (210) once the lost SNMP trap is handled. The process is repeated until the list of the lost SNMP traps is reduced to zero. In the event that the number of lost SNMP traps are more than the list of the historical information appended to the SNMP trap, the system will define the list number for historical trap information required (211), and retransmission request is sent (212) to the network element (10) for obtaining the required SNMP trap OIDs, and necessary actions can be taken to process the SNMP trap. Figure 4 is a diagram showing the process for retransmitting a lost SNMP trap. The network element (10) receives the retransmission request (301) from the network management station (20). The network element (10) obtains the list number for the historical trap information (302). The requested SNMP trap is extracted (303) and then retransmitted (305) from the trap transmission database (13), wherein the retransmitted SNMP trap also contains the list of OID of the previously transmitted SNMP traps (304). In a preferred embodiment, the retransmitted SNMP trap is not stored again in the trap transmission database (13).

In an exemplary embodiment as shown in Figure 5, the transmission between the network element (10) and the network management station (20) is shown. It is shown that the SNMP trap with sequence number 3 is lost and is detected when SNMP trap with sequence number 4 is received. However, the OID of the SNMP trap with sequence number 3 can be retrieved from the SNMP trap sequence number 4. In this particular example, the retransmission is not required and therefore no retransmission request is sent. If, however, additional information is needed, the retransmission is request is sent for retrieving the lost SNMP such as the SNMP trap sequence number 6. In a further scenario, a plurality of SNMP traps with consecutive sequence number are lost, namely the SNMP traps with sequence number 9, 10, 11 , 12, and 13. The receipt of SNMP trap number 14 would allow the extraction of OID for SNMP trap number 13 and the SNMP trap number 13 can be further processed. The network management station (20) however still needs to retransmit SNMP trap number 12 with three OIDs of the previously transmitted SNMP traps. In this way, all the lost SNMP traps number 9, 10, and 11 are recovered and processed.

It will be apparent to those skilled in the art that various changes and modification may be made therein without departing from the principle of the invention or from the scope of the appended claims.