FPGA Implementation of Lookup Algorithms

Presenter : Shi-qu Yu

Email : P76001158@mail.ncku.edu.tw

Date : 2011/08/31

OutlinePOLP[2] and BPFL algorithmBPFL Search EnginePOLP Search EnginePerformance

POLP algorithmPOLP:Parallel optimized linear pipeline algorithmMain idea:

Split the original binary tree into non-overlapping subtrees that are distributed across P pipelines.

Chose Pipeline:Base on the first I bits of the IP address.

PFL Algorithm

BPFL AlgorithmAn extension of the PFL algorithmAdvantage of BPFL:

Frugally uses the memory resources so the large lookup tables can fit the on-chip memory.

Next-hop information->External memoryLookup table->On-chip memoryThe subtree prefixes are stored in the corresponding balanced

trees(PFL:register)

BPFL Algorithm(cont.)External memory is accessed only once at the end of the

lookup when the next-hop information is retrieved.The on-chip lookup table is organized as a binary tree divided

into levels that are searched in parallel.If the substree is sparsly->Only indices of existing nodes are

kept.

BPFL Search Engine

BPFL search engine top-level

BPFL Search Engine (cont.)

Find the subtree at this level. Process prefix search.

BPFL Search Engine (cont.)

Subtree search engine at level i.

BPFL Search Engine (cont.)

Subtree search engine at level i.

BPFL Search Engine (cont.)

Prefix search engine at level i.

BPFL Search Engine (cont.)

POLP Search Engine

POLP Search Engine(cont.)

Pipeline structure.

POLP Search Engine(cont.)

Stage i structure.

PerformanceAltera’s Stratix II EP2S180F1020C5 chip [10].The SRAM memory is used as the external memory.

Performance(cont.)

BPFL(DS=8)

Performance(cont.)

POLP(I=16)

Performance(cont.)

BPFL(DS=8)

Performance(cont.)

POLP(I=16)