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Design and Implementation of Network Management Based-on SNMP |
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| 作者：Wu Tao, Zhao Hai-bao School of Information Technology and Engineering, Tianjin University of Techno |
| 來源：本站原創 |
| 更新時間：2010/5/20 14:10:00 |
| 正文： |
Abstract: This paper designs a SNMP-based data collection system and provides a variety of Java-based technical support to implement the four layers of the system. Depending on the characteristics of the data required to be collected, this paper makes full use of the Java multi-thread advantage and accomplishs a multi-thread trap-dominating polling process.
Keywords:SNMP ;network management ;data collection ;multi - threads
1 Introduction
With the widespread use of the network, its structure and size is becoming respectively more complex and enormous, resulting in network management to be more prominent. The data collection, which the network management functions are dependent on, is also becoming more important. Data collection system collects all the managed objects in the managed devices and processes them for various network management applications. SNMP[1-3]has become the actual network management standard supported by many network device vendors. Because of its simplicity and compliance of standard function interface, it is now the commonly used protocol for network management. This paper designs an SNMP-based data collection system and uses a variety of Java-based technical support to implement the four layers of the system. In this system, according to the characteristics of the data to be collected, multi-threads are created to access various managed devices, with the result of enhanced efficiency in data collection and reduced collection of redundant information.
2 SNMP Protocol
The Simple Network Management Protocol (SNMP) is an application-layer protocol that facilitates the exchange of management information between network devices. An SNMP managed network consists of three key components: managed devices, agents and network-management system (NMS).
A managed device is a network node that contains an SNMP agent and resides in a managed network. Managed devices collect and store management information and make this information available to NMS using SNMP. Managed devices, sometimes called network elements, can be routers, access servers, switches, bridges, hubs, computer hosts or printers.
An agent is a network-management software module that resides in a managed device. An agent has local knowledge of management information and translates the information into a form compatible with SNMP.
An NMS executes applications that monitor and control managed devices. NMS provides the bulk of the processing and memory resources required for network management. One or more NMSs must exist in any managed network. When NMS issuing a request, the managed devices return responses to it. This behavior is implemented by using one of the five protocol operations: Get, GetNext, Trap , GetBulk and Inform.
3 System Design
3.1 System Objective
Data collection system is a relatively independent module, with a main task of providing necessary data for network management system and sending control commands from the network management system to the managed objects. Taking the overall framework of the system design into account, data collection system must meet the following requirements[4]:
（1）Data collection system is completely designed according to the actual needs of network management system. It exchanges data with other funtions of the management system such as network topology discovery. It should be high efficiency and less cost in development.
（2）It should comply with the SNMP protocol.
（3）During design, it is necessary to take consideration on the changes in versions of SNMP protocol. Most importantly, the system doesn’t need to change when the SNMP protocol updates[5].
3.2 System Architecture
The data collection system designed in this paper is structured into interface layer, middle layer, data layer and process layer of four levels. Interface layer, including data collection interface and customization interface, provides interaction to the user. The middle layer provides the JDBC database interface to access back-end database, and implements the SNMP protocol stack. The middle layer directly serves for upper layer in a manner that is acceptable for the applications. Data layer is mainly composed of back-end database which records all kinds of information involved by the system and it is also the hub of information exchange. Data layer stores the modeling results from customization interface, such as classes, objects, ports, expressions, and so on. Process layer is formed by a number of data collection threads, the maximum number of which are set by the user through data collection interface. All of these threads cooperatively perform data collection task. Information received from managed devices by data collection layer is delivered to milldle layer and processed by middleware, part of the result of which is historical data that is stored in a database for the upper layers to apply. The concrete realization of the process is shown in the figure below[6].
Procedure Description
（1）First, the customization interface defines data types (scalar or tabular), objects and port numbers. It also adds new universal performance expressions and new equipment performance expressions in line with the data requested by management functions such as: topology discovery, performance monitoring and other network management functions. Then passing through the middleware, this information is stored into the database. Interface layer constitutes one or more client-sides where multiple clients can simultaneously operate the database; however, only one client with the written permission is allowed to add new expressions, classes, objects, and port numbers for configuration.
（2）When a request is issued to view information, the data collection interface is exposed on the page. According to the request which specify the target IP address, the target community name, and the managed object ID, the data collection interface initiates a process through the middleware to obtain the data format customized by the customization interface from the database. Incidentally, interface layer performes the functions of store, print and display after receiving the real-time data processed by the middleware in the step fourth.
（3）Then the corresponding procedures in the data collection interface pass the request along with the data formats obtained previously to the collection program in the process layer to get the required information. Collection procedures using the SNMP protocol collect data in appropriate parameters from the managed devices on the basis of the data formats.
（4）After acquiring the data from the devices, the collected data is delivered to the middleware for processing, and then the processed data is divided into two categories: real-time data and historical data. The real-time data is directly sent to the interface layer for use while the historical data is saved to the database for later calls which is done by renewing related table through the middleware.
4 Implementation
4.1 Interface Layer
Interface layer communicates with the middle layer, in which the interaction is initiated by a user. Interface layer mainly employs Eclipse to develop data collection interface and customization interface , while Java Applet are used to display interactive control information to provide an excellent interface for network administrators. As the middle module of GUI, Java Applet can flexibly adjust to the change of network configuration and work for a variety of operation request.
4.2 Middle Layer
The middle layer accesses the back-end database using the java-database-connector.jar through the JDBC database interface, and implements SNMP protocol stack using snmp4j.jar package to provide compatible services for interface layer. Middle layer can be a stand-alone server, or it can share the same machine with the database. As the Middle layer interconnectes the user interface and database which may be located in seperated machines; user interface does not generate a database query commands but can only access to the middleware which generates database query commands, as a result, multiple users can simultaneously access the same data.
4.3 Data Layer
Data layer uses MySQL technology to implement the database. Using JDBC connections, it enables Java Applet to directly access the database using the middleware. For example, when Java Applet of the interface layer excutes SNMP operations, it invokes classes and methods in the database through the middleware, then database sends the corresponding results to the interface layer.
4.4 Process Layer
Data collection is done in two ways: by actively accessing managed objects and passively receiving alarm messages. Actively accessed managed objects are divided into static information and dynamic information. Static information does not change with currently operating device. It generally remains the same if the manual settings does not change. Dynamic information changes along with the device performance and operational status’s change. For collecting dynamic information, it is necessary to conduct polling managed objects in managed devices, in which we should also considere the number of managed devices to determine the frequency of data collection according to the actual network bandwidth resources. If we use serial method to access all managed objects in all devices, it will take a very long processing time due to the large number of objects. Sometimes it may even take beyond the established acquisition cycle, which may cause the collection process not be carried out normally. To solve this problem, multi-threading method is intruduced, where collection process uses one main thread to control many sub-threads for data collection. Using separate sub-threads to access the same managed device, not only can it guarantee to completely access all managed objects in a certain cycle（period of time）, but also makes the various sub-threads to maintain their relative independence without disturbing one another.
（1）Warning information receiving sub-thread
For passively receiving alarm messages, collection process opens a separate sub-thread to specifically monitor trap port and to receive and manage all of the alarms from the network management agent (Trap message). In the network management functions, such as performance management, fault management, or security management[7], alarm mechanisms are very important. Here we mainly use the SNMP Trap mechanism to achieve real-time alerting capabilities.
（2）Static information polling sub-thread
For static information collection, collection process opens a separate sub-thread to carry out information collection. Since the static information does not often change with the operation of the device, there is no need to repeatedly access such information. In this sub-thread, the static managed objects are only acessed once from which the management information collected are saved into a database. Application process just accesses local database for such data , so there is no need to access the non-real-time information frequently. This can reduce the redundant information storage. Changes in static information are generally caused due to manual configuration of managed device, therefore tracking configuration operation is required to timely update information correspondingly.
（3）Dynamic information polling sub-thread
Dynamic information constantly changes and is the focus of data collection. Collection process opens a management thread responsible for polling dynamic information. A certain time interval is required for polling dynamic information in real time (usually 3--5 minutes). The amount of management information necesserly collected are very large, therefore a number of polling sub-threads are used to parallelly access their own subset of managed objects. This helps to avoid
the long-period caused by the serial method and it can ensure to complete polling task within a specified time interval.
5 Conclusion
This paper briefly discusses about the theory of data collection and studies the objective of data collection system. Then it designs an data collection system and provides the implementation method. The experiment indicates that the system designed in this paper can run smoothly and obtain good effectiveness in the application of network management system.
References
[1] J. Case. Simp le Network Management Protocol ( SNMP).RFC1157
[2] J.Case. Introduction to Version 2 of the Interner – standard Network Management Framework. RFC1441
[3] J.Case. Management Information Base for Version 2 of the Simple Network Management Protocol ( SNMPv2 ). RFC1450
[4] Netak L D, Kiwelekar A W. Efficient Network Management using SNMP[J]. Journal of Network and Systems Management,2006,14(2):89-94.
[5] Jithesh Sathyan, Naveen Unni, Saurav Kantichandra, Prashanth Gopinath. Defining an Optimized Management Protocol for Next Generation Packet Networks[J]. IEEE,0-7803-9410-0,2006.
[6] LI Xia, WANG Jianmin. Implementation of Accounting System Based on SNMP[ J ]. Computer Knowledge and Technology, 2005 (12) : 67-68(in Chinese).
[7] Schonwalder J, Pras A, Martin-Flatin J P. On the Future of Internet Management Technologies[J]. IEEE Communications Magazine,2003, 41(10): 90-97.
Biography:
WU Tao (1985 - ),Male (The Han Nationality),BuoZhou of An Hui Province,Tianjin University of Technology and Education,Postgraduate,Major,Computer Applications Technology
ZHAO Hai-bao (1983 - ),Male (The Han Nationality),BinZhou of Shan Dong Province,Tianjin University of Technology and Education,Postgraduate,Major,Computer Applications Technology
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