Research And Implementation Of Rapid Spanning Tree Protocol On Vxworks

Industrial Ethernet has higher requirements of network links’ reliability, it usually needs redundant links to increase network’s viability. However, the Layer2link redundancy between switches will form network loops, and produce "broadcast storm" affecting normal communication capability. Spanning Tree Protocol aims to solve network loops, and dynamiclly manage the redundant links. Rapid Spanning Tree Protocol (RSTP) optimized the spanning tree algorithm, and added state machine processing mechanism to greatly reduce the convergence time. The rapid convergence feature of RSTP welly meets the industrial Ethernet link reliable and rapid recovery needs, and thus was widely used. Meanwhile, to ensure the real-time and reliability of the operation environment of RSTP, an embedded real-time operating system VxWorks was also been used.In this paper, we investigated real-time task scheduling mechanism and software layered model of Vx Works, and study the RSTP principles and mechanisms of rapid convergence, the state machine model was aslo introduced. In terms of realization, we use Vx Works task mechanism to establish a dual-task processing and interactive structure to make message and timing modules running concurrently, meanwhile, we use network layered architecture to provide a compatibale RSTP software upon different phisical chips, and it can be easily transplant between them via a multiplexer (MUX) layer. In addition, this paper designed network management feature and provide a solution of the conflict between port aggregation and loop cutting, and we also adding two port state machine into standard RSTP Algorithm to deal with the problem bring from port state change, so that the protocol software can possess more reliability and better meet the needs of practical application. This paper followed the general software development procedure, including research, design, coding and testing. By running in the target development board, we complete the design goals and meet all the requirements of the RSTP software.