The Software Design And Implementation Of Layer3Switching Based On Vxworks System

For reasons of safety and management in the construction of large LAN, we need to use VLAN tech to subdivide large LAN into small LANs, depending on their needs or geographic features. Communication between VLANs must be done using a router. With the development of networks and a variety of services and applications, users are more and more focusing on the requirement of bandwidth and QoS. Due to the limited number of router ports and slower routing speed, traditional routers limit the net scale and access speed of the network during inter-VLAN communication. Layer3switching tech is a combination of layer2switching and layer3routing tech, it owns wire-speed forwarding capability with "once routing, multiple switching" by using high-speed forwarding chip. The use of layer3switch improves internal LAN routing and switching capability and the network scalability, while reducing the costs.In this paper, the author designed and implemented the RIP routing protocol and forwarding table maintenance (FTM) software in layer3switch. RIP provides dynamic routing learning function, and FTM software makes sure the data is forwarded with wire-speed in third layer. In the design and implementation of RIP, the author used the real-time multitasking communication and highly optimized semaphore mechanism in VxWorks to improve the RIP task process. In the design and implementation of the FTM software, the author proposed to reserved space-based selecting moving algorithm, having solved the problem of large-scale moving entries due to frequently operating the table, improved the efficiency of moving entries. Considering the limited capacity of forwarding table, the author implemented LRU replacement algorithm to add entries so as to improving the fairness of the entry replacement. For the delivery mechanism of routing messages, the author implemented efficient message queue communication mechanism in VxWorks system, to make sure the stability and instantaneity of routing message delivering. In the end, the L3switch passed through the test of conformance testing, interoperability testing, and forwarding performance testing by network analyzer test set. The test results indicate that the performances of the layer3switch met the requirements.