Research And Design On An Accurate Lookup Method Based On Sdram

With the rapid development of network technology, the Internet has become one of indispensable parts of people’s life. Network traffic doubles the amount every six months. With the development of optical communication technology, the link transmission rate is no longer the performance bottleneck of network technology. Network lookup and forwarding technology has became the main constraint of the development of the Internet. To deal with inflexible management and uneven traffic scheduling problems, Software Defined Network (SDN) is proposed. In SDN, the lookup and forwarding information is maintained in a flow table. Most existing high-speed lookup method does not perfect to apply to SDN flow table lookup. In this paper, accurate lookup methods used in OpenFlow switches are researched.The thesis firstly investigated the exiting high-speed lookup method. Then an accurate lookup method for OpenFlow switch based on SDRAM is proposed combining the prefix routing lookup methods. This method includes the hardware preprocessing module and off-chip lookup tables. Within the hardware preprocessing module, this paper proposed a parallel Bloom filter architecture to reduce the necessary off-chip accesses. The number needed for a successful lookup could be reduced to nearly one after a reasonable allocation of hardware resources and improvement of Bloom filters. AS SDN flow table requires scalable and parallel lookup, this paper proposed a configurable parallel Bloom filter and a two-stage pipeline Bloom filter to reduce the on-chip processing power. When configured properly, you could save up to80%of power consumption. With the lookup table designed in off-chip memory, this paper studied the off-chip memory SDRAM access reorder mechanisms to improve bus utilization. Compared to the conventional burst scheduling mechanism, the BIS mechanism proposed in the paper could improve the utilization by25%. According to the pattern of OpenFlow flow tables and SDRAM device characteristics, a memory address allocation method is designed. Finally, this paper studied the design of the control principle SDRAM and implemented a SDRAM controller using FPGA.As the key protocol of SDN, the flow table look-up in the OpenFlow enable people to control the network more flexibly. However, looking up several tables brings new challenges to the high-speed look-up algorithms. So research in the area has great significance.