Based On Hop Count Of Passive Lan Network Layer Topology Discovery Algorithms

The network topology discovery technology, performing the function of mapping out the topology structure of unknown network timely and accurately, can simplify the original complex network management. Hence the network scale has expanded gradually and has attracted more and more attention from network managers as network structure becomes more and more complex today.The thesis is organized as follows:Firstly, the development of technology of network topology discovery at home and aboard is introduced. Then Several traditional algorithms of network topology discovery is expounded and their advantages and disadvantages are analyzed. In order to discover LAN network layer’s topology structure, a hop-count-based algorithm of passive network topology discovery facing network layer equipment of LAN is proposed in the thesis. The algorithm makes good use of the hop-count representing distance between the source host node and probe node to divide the subset in the to-be tested network, and then through analyzing the ARP messages of various subsets, IP and MAC of network equipments in every subnet are gained. Compared with initiative measuring method, this method also succeeds in obtaining IP address of host nodes in every subnet without exerting additional flow to the to-be tested network, in other words, this method is a passive one. During the process of discovery, some problems are solved in this thesis, such as the selection of location of the probe nodes in LAN Network, the identification of the IP address of source host nodes in LAN Network, the division of subsets in LAN network, the recognition of router’s interface in every subnet and how to merge them into a complete router, and how to find out the connections between various subnets.In order to validate the effectiveness and accuracy of the algorithm proposed,two network simulation experiments have been done in network simulation software NS3in the thesis.In the first simulation,a LAN model is constructed randomly and simulated repeatedly while it’s simulate-time is changed in every simulation. In the other simulation,keeping the simulate-time as a constant,and then the simulation experiments have been done repeatedly,while the network topology of the LAN model is changed in every simulation.Then the method proposed in this thesis is used to discover the topology of the constructed LAN model. Finally the effectiveness and accuracy of this passive algorithm are validated by comparing the result of network topology discovery with the topology structure of constructed LAN model. Moreover, after repeated simulation experiments, the results show that the algorithm can perform well the task of discovering the topology of LAN network layer equipments.