Research And Implementation Of SNMP-Based Topology Probe System For Switched Ethernet

Network topology probing is the foundation of network management and maintenance:it gains and stores all kinds of information of the network, analyzes and calculates the network topology, shows the network status, and serves the upper-level system and users. With the development of computer network technology, the scale of modern network is becoming bigger and bigger, the structure of the network is also more complex, which makes topology probing becomes more difficult. As the most common form of network, Switched Ethernet normally is the basis of large-scale network, such as Campus Network of an enterprise, Mobile Bearer Network of the operators, etc. Switched Ethernet has a series of characteristics, for instance, large number of devices, complicated connections, different kinds of device, plenty of running protocols, etc. These make topology probing in Switched Ethernet much more difficult. Hence, how to get the physical topology and the VLAN topology of Switched Ethernet quickly and efficiently is a burning question at present.First of all, detailed analysis and comparison of serveral physical topology discovery algorithms are described in this paper. After considering the characteristics of Switched Ethernet and the requirements of the topology probing system, a physical topology discovery scheme which is used SNMP as the topology discovery tool is proposed in the paper. This scheme synthesizes serveral topology discovery algorithms, in order to achieve discovery the topology rapidly and completely. The basic idea of this scheme is using the spanning tree information of the device as the primary method, and using the information of the link layer neighbor protocols as the supplement. To achieve collecting the spanning tree information as complete as possible, serveral vendor private MIBs are used in this scheme.At the same time, VLAN protocols in Switched Ethernet are deeply studied and MIB information of two main VLAN protocols is also described in the paper. After that, a complete VLAN topology discovery method is proposed in this paper.Finally, the design and implementation of topology probing prototype system are described in the paper. A mixed network which is builded by simulation system and physical devices is used to test the prototype system. Not only the algorithms and functions of prototype system are proved in the system testing, but also the system performance is estimated. The results of system tests show that prototype system can discover the physical topology and the VLAN topology rapidly and correctly. Also, it dose not increase a heavy load to the network.