Key Technologies Research On Forwarding Table Management Software Of Access Converging Router

Forwarding engine is the most important part of the Router, its work is to route and forward the IP packet. As a subsystem of the Router software system, the core task of forwarding software is to establish and maintain the forwarding table. This dissertation is devoted to the researches of the key technologies to the design and implements the ACR forwarding software according to the requirements of 863 project: Research on system performance and key technologies of large-scale Access Convergence Router (ACR), and mainly studies the three primary parts: the forwarding table software modules and tasks partition, the forwarding table management algorithms and the implementation, the task scheme and the memory management. The main works of this dissertation are as follows:1. The software and hardware environment of the ACR forwarding subsystem are introduced, the forwarding software functions are described, the software modules and the tasks are partitioned. This part is the base for forwarding software design.2. This dissertation classifies and compares current routing lookup algorithms, and points out the shortage of current routing lookup scheme, which provides new ideas to the ACR forwarding design.3. By analyzing the current TCAM updating algorithms, this dissertation presents a new scheme: Reserving empty space and selective updating algorithm based on hash table. The scheme which supports both IPv4 and IPv6 protocol is implemented in the ACR produced by NDSC, experiment results show it works well.4. By pointing out the shortcoming of the task scheme in VxWorks OS, this dissertation designs a two stage scheme method based on the "pseudo-thread". By analyzing the shortage of the previous forwarding table management scheme when the updating messages arrive burstily, the dissertation puts forward a new two level forwarding table management scheme. Simulation results indicate that the algorithm works efficiently under the bursty case.5. To decrease the OS cost and protocol cost when sending data, and transmit data with high speed, the dissertation adopts "zero copy" message queue to decrease the delivered information, and presents the memory management scheme to increase the efficiency to management memory, offers theories and technologies for the software to run with high efficiency and credibility.6. At last, the dissertation gives some measures to improve the forwarding software subsystem in aspects of the consistency between the routing table and the forwarding table, the redundancy of the ICMP messages, the safety and the robust of the software system.