Simulation and Analysis of OSPFv2 DR Election Based on GNS

Designated Router (DR) is the key for the quality of an Open Shortest Path First (OSPF) network and it enables a reduction in the number of adjacencies, which in turn reduces the amount of routing protocol traffic and the size of the Link State Database (LSDB). In this paper, we analyze the principle of OSPFv2’s DR election algorithm and carry out the simulation based on GNS3. The simulation can provide a reference for building an OSPF network. In the simulations, we focus on two types of DR Election process: Normal DR Election and DR reelection. Experimental results show that the election of DR and BDR can reduce the amount of OSPF traffic and ensure an orderly transition from Backup Designated Router to Designated Router. However, through the simulation we also learn that lots of unnecessary DR election operations are executed, which consume the routers’ CPU resource and occupy their processing time. To improve the election algorithm, we offer several modifications. We detach and subdivide the NeighborChange event that invokes the election algorithm into more specific granularity. Through these measures, the DR election algorithm is expected to dispense with the extra election, reduce network convergence speed, and thereby improve network performance. Keywords-OSPF; DR ; BDR; DR Election; GNS