Research On Network Topology Discovery Method Based On OSPF And SNMP

As an important part of network management system, network topology discovery is an important aspect of network detection and research. Especially with the scale of network is getting bulky and complex, network topology discovery has become the basis of efficient network management. Presently, how to rapidly and accurately discover network topology has been the focus and hotspot of the related research field. The traditional network topology discovery method was basically based on the SNMP protocol, but the SNMP itself exits the problems, such as poor real-time, big spending, etc. Because OSPF protocol has the advantages of fast convergence and small cost control. So this paper puts forward a network topology discovery method which is based on OSPF and SNMP, the method can respectively discover topology structure of network layer and link layer, based on the method, a network topology discovery system is designed and implemented.The main work in this paper is as follows:A discovery algorithm for network topology based on OSPF is proposed. Aim at the existing problems of network layer topology discovery method based on SNMP which is active detection method, such as poor real-time and increasing network load, etc, a discovery algorithm for network topology based on OSPF is proposed. The algorithm applies the way of passive monitoring to obtain the link state update packet of OSPF protocol through Jpcap, and analyzes the topology information contained in the Router LSA and Network LSA, which can discover the network topology. Simulation result indicates that the algorithm can rapidly and completely discover network layer topology.A link layer topology discovery algorithm based on SNMP is proposed. Aim at the existing problems of link layer topology discovery method based on SNMP, such as redundant computing and low efficiency, etc, a link layer topology discovery algorithm based on SNMP is proposed. The algorithm adopts the idea of hierarchy and describes the connection between switches as a tree form. Then the connection of each switch is established for every layer according to a top-down manner. By improving the conditions of the connection between switches, combining with two key techniques to improve the efficiency of topology discovery: 1) Using thread pool to find the active devices and judge their types, which can resolve the problem of long time waiting packets in the way of single thread, and improves the discovery speed. 2) Using hash table to store the MAC addresses contained in the switch ports, the speed of ensuring the connection between devices can be improved by the way of hash search. The experimental result indicates the algorithm is better than the algorithm before improvement on discovery efficiency, in addition, the Hub in the network can also be discovered.A network topology discovery system is designed and implemented. The system uses three-tier application design: topology information can be obtained by data layer, and service layer can give a topology result based on the above two topology discovery algotithms, combining with JGraph display layer will show a clear network layer and link layer topology graph for users. The effectiveness of the proposed algorithms are verified after system testing in a real network environment.