Perfect Hash-Based Routing Lookup for LEO Constellation Backbone Network

The performance of packet forwarding mainly relies on the routing lookup (RL) in high-speed routers and switches. Due to the network topology change and the limited resource on aerospace devices, the RL strategy for low Earth orbiting (LEO) constellation backbone networks should be specifically designed. Targeting lower resource consumption, we first propose the perfect hash-based RL, including a perfect hash function (PHF) for metarule space compression plus random access for the output interface. A satellite perfect hash function (SPHF) algorithm is proposed to generate efficient hash functions with limited storage. For 10 000 randomized keys, the SPHF algorithm constructs 50-Kb PHFs in 3.05 ms with 538 Kb storage. Then, we design the routing-oriented hash function (RHF) algorithm by fusing the perfect hash and RL, and optimize RHF toward the hardware implementation. The RHF algorithm is robust to different RL scenarios. In the field programmable gate array (FPGA) (xc7k70t-fbv900-1) experiment with 10 000 32-bit metarules and four output interfaces, a typical RHF algorithm (RHF1) costs only 13.2 ns and 1429 equivalent look-up-table (LUTs) to lookup each packet under 312.5 MHz clock frequency. Compared with most advanced ternary content addressable memory (TCAM)-based implementations, RHF1 reduces the storage and logic resources by at least an order of magnitude while keeping comparable lookup latency in the same FPGA Chip. This article provides a design mentality for the RL of low Earth orbiting constellation backbone networks.