Perfect Hash-Based Routing Lookup for LEO Constellation Backbone Network

Abstract

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 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 10000 randomized keys, the SPHF algorithm constructs 50-Kb PHFs in 3.05 milliseconds with 538 Kb storage. Then we design the Routing-oriented Hash Function (RHF) algorithm by fusing the perfect hash and RL, and optimize RHF towards the hardware implementation. The RHF algorithm is robust to different RL scenarios. In the FPGA (xc7k70t-fbv900-1) experiment with 10000 32-bit metarules and 4 output interfaces, a typical RHF algorithm (RHF1) costs only 13.2 ns and 1429 equivalent 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 paper provides a design mentality for the RL of LEO constellation backbone networks.