MULTI-WAY PIPELINING FOR POWER-EFfiCIENT IP LOOKUP

Author: Weirong Jiang and Viktor K. Prasanna

Publisher/Conf.: IEEE GLOBECOM 2008

Speaker: Han-Jhen Guo

Date: 2008.12.17

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OUTLINE

Background and Related Work Proposed Scheme

introduction of proposed scheme hybrid SRAM/TCAM-based partitioning fine-grained node-to-stage mapping

Performance

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BACKGROUND AND RELATED WORK

Uni-bit trie

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Leaf pushing

Proposed Scheme- Introduction Of Proposed Scheme

Multi-way linear pipeline architecture (P=4)

each pipeline stores a portion of the routing table hybrid SRAM/TCAM-based partitioning scheme

ensure that pipelines contain exactly equal numbers of trie nodes

fine-grained node-to-stage mapping scheme within each pipeline balance the memory distribution over pipeline stages 4

Proposed Scheme- Hybrid SRAM/TCAM-based Partitioning

1. Prefix expansion

initial stride larger, smaller subtries → can help balance the memory

distribution across stages when mapping nodes to stages within a pipeline

more prefix duplication (a prefix may be copied to multiple subtries)

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initial stride (I)

Proposed Scheme- Hybrid SRAM/TCAM-based Partitioning

2. Post-order split ensures that each pipeline contains ceiling of

(total nodes of subtries / number of pipelines) nodes (except the last one pipeline) sort the subtries obtained after prefix expansion in

decreasing order of size

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ceiling of (3+11+1+3) / 2

Proposed Scheme- hybrid SRAM/TCAM-based partitioning

3. Index table implementation

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based on I

remaining subtries

priority(SRAM_B) > priority(SRAM_A)

Proposed Scheme- fine-grained node-to-stage mapping

1) Leaf reduction

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subtries in pipeline 1

after leaf reduction

Proposed Scheme- fine-grained node-to-stage mapping

Eg. of node-to-stage mapping with pipeline 1

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Proposed Scheme- hybrid SRAM/TCAM-based partitioning

Index table implementation

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address of the subtrie’s root in the 1st stage of pipeline

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PERFORMANCE

Node distribution over 8 pipelines results for 16 routing tables

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partitioning scheme achieved a balanced memory allocation among the eight pipelines

PERFORMANCE

Node distribution over 25 stages in the 8-way pipeline architecture

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there were few nodes at the top levels of any subtrie→ unbalanced at first several stages each pipeline

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