TCAM Block Segmentation for Entry Insertion Moves

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Solution Overview

Problem

Ternary Content Addressable Memories (TCAMs) are expensive and power-intensive due to their larger silicon area requirements and higher power dissipation compared to Static Random Access Memory (SRAM), limiting their usage in network switches, and existing methods for adding entries in TCAMs often require extensive relocation of existing entries, increasing the number of moves needed.

Innovation Solution

Dividing the TCAM into blocks of square root size, using circular priority encoders and hierarchical thermometer decoders to minimize the number of moves required when adding new entries by optimizing the placement and relocation within these blocks, reducing the overall number of entries that need to be shifted.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If TCAM is used to store match entries in network switches, then matching speed and functionality are improved, but silicon area and power consumption increase significantly

Engineering Contradiction:

Improvematching speedVSAvoidsilicon area

Core Design Contradiction:

SpeedVSArea of stationary object

Solution Approach 1:

The TCAM is divided into multiple banks, with each bank containing several blocks of equal size. This segmentation allows the TCAM to be organized into manageable units that can be independently addressed and managed, reducing the overall silicon area required while maintaining matching functionality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a hierarchical addressing scheme that adds dimensional organization to the TCAM structure. By organizing TCAM entries across multiple banks and blocks with specific addressing patterns, the system achieves efficient matching without requiring a single large contiguous memory array, thereby reducing silicon area.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Adaptability or versatility

If existing methods are used to add entries in TCAMs, then new entries can be inserted, but extensive relocation of existing entries is required increasing the number of moves

Engineering Contradiction:

Improveentry insertion capabilityVSAvoidnumber of moves required

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

By dividing the TCAM into banks and blocks, the patent enables localized entry insertion within specific blocks rather than requiring global relocation across the entire TCAM. This segmentation allows new entries to be inserted with minimal disruption to existing entries, significantly reducing the number of moves required.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent implements vacancy management mechanisms that maintain empty slots in advance within blocks. This preliminary preparation of vacancies allows new entries to be inserted directly into pre-prepared slots without requiring extensive relocation of existing entries, thereby improving productivity during entry addition operations.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS9484095B2TCAM providing efficient move contents operation

Publication Date: 2016.11.01 TEXAS INSTRUMENTS INC

AI summary

An embodiment of the invention includes a Ternary Content Addressable Memory (TCAM) that includes a group of TCAM block. Each TCAM block stores a number of match entries. Each TCAM block is ranked in priority order. The TCAM also includes a group of TCAM headpointers. There is a TCAM headpointer coupled to each TCAM block. The TCAM headpointer indicates the highest priority match in the group of match entries in a TCAM block. The match entries within a TCAM block are prioritized in circular priority order starting from the highest priority match.