Study On Key Technologies Of Topology Discovery In Data-link Layer

With the development of computer network technologies, the scale of computer networks is getting bulky and complex and the heterogeneity of networks is getting higher and higher. The technique of network management has also become a very important issue. Network automatic topology discovery as an important part of network management has special research significance. In addition to network management, network automatic topology discovery can be used in many new application areas such as server locating, network planning, etc.At present, most of the network automatic topology discovery algorithms are developed to discover IP layer topology based on routing tables obtained from SNMP. But, more and more data-link layer devices as switches are deployed in IP networks. Such devices become subnet segmentation. Thus, more and more network infrastructures are invisible to a layer-3 mapping, so present layer-3 network automatic topology discovery algorithm can't satisfy network management requirement. The data-link layer topology discovery becomes an indispensable part of a network automatic topology discovery system. Some unique difficulties of data-link layer topology discovery make it fall behind the research of layer-3 network automatic topology discovery. So, it has become the focus and difficulty of the research on network automatic topology discovery.In this thesis the current achievements of data-link layer topology discovery are analyzed in detail, their shortages in popularity and integrity are indicated. The implementation of discovery based on address forwarding tables and spanning tree protocol is systematically summed up. Respective deficiencies of the two algorithms are compared. A new data-link layer topology discovery algorithm integrating the above two methods is proposed. The new algorithm can discover redundant physical connections.In the implementation of the algorithm, the concept of edge switch is introduced. So the data-link layer topology discovery is divided into switches network topology discovery and hosts network topology discovery. Thus, the topology discovery process is simplified. Meanwhile a design of topology map display is presented, in which the map jitter problem was solved. The application of virtual switch makes the topology map more hierachical.A data-link topology discovery prototype system is developed for research. The feasibility of the data-link topology discovery algorithm presented in this paper was fully verified by the prototype system.The final test results show that the data-link layer automatic topology discovery algorithm designed in this paper worked well in single subnet management domain. The further research work will be the topology discovery in multi-subnet management domain and the topology discovery in virtual local area network. Besides, how to combine presented algorithm together with IP layer topology discovery is also a challenging issue.