Research And Implementation Of Link-layer Topology Discovery Based On AFT

Network topology discovery is foundationof network management andlink-layer topology plays an important part onthe whole network topology.However, withthe variation of link-layer devices,their transparent characters and thecomplexityof multi-subnet networks, it becomes an emphasis and difficulty of network topology research to discovery the link-layer topology. Through analyzing mainstream link-layer topologies and algorithms, this paper presents an improved link-layer topology discovery for the complex mulit-subnetnetworks.At first, four sorts of link-layer topology discovery algorithms are analyzed which are based on private protocols, spanning tree protocol, probe packets and address forwarding table. And the algorithm based on address forwarding table is found to be extensively applicable.Verified by theory and practice in actual network environment, it is more feasible to create complete downlink address forwarding table than complete address forwarding table.Thus, our research puts forward a topology discovery algorithm on the condition of complete downlink address forwarding table. The algorithm based on shortest path is actually an improvement to algorithm which is presented by Yigal Bejerano.This algorithm utilizes the complete downlink address forwarding table to construct shortest paths which are between switch devices in the same subnet, thenoptimizes these paths with four port adjacencyjudgment rules, so that every path becomes port sequence which constitutes the whole link-layer topology. Compared with current studies, our algorithm can be well applied on multi-subnet networks and reduce algorithm complexity. At last, this algorithm has beenappliedon campus network of some Uinversity for testing,which is implemented by VC++programming method based on SNMP. Our algorithm can discovery the link-layer topology accurately.Verified by the theory and practice in actual network environment, the algorithm based on the complete downlink address forwarding table with shortest paths can discover the link layer topology for complex multi-subnet networks accurately. Our researchhas a strong practical significance and promotional value.