Multi-Functional Match Cells for Packet Processing Range Matching
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Solution Overview
Problem
Conventional packet classification operations in high-performance routers are inefficient due to high power consumption and reduced capacity in ternary content addressable memories (TCAMs) when handling range filters, which require multiple entries for each range to be matched, leading to reduced effective capacity.
Innovation Solution
Integrated circuit comparators that determine non-strict inequalities between operands, allowing for efficient range match operations using n-bit comparator cells configured with MOS transistors to generate control output signals encoding inequalities, and multi-functional match cells that operate as range match cells, NOR-type, or NAND-type CAM cells depending on operand masking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple TCAM entries are used to represent each data pattern with range fields, then range matching capability is improved, but effective capacity of TCAM is reduced by a factor of two or more
Solution Approach 1:
The patent applies multi-functionality by designing a single TCAM entry to perform multiple functions: it can match both exact values and range values simultaneously. The range check circuitry integrated within each TCAM cell enables the same hardware structure to handle both precise matching and range matching operations, eliminating the need for separate entries for range operations.
Solution Approach 2:
The patent merges the range check functionality directly into the TCAM cell structure. By combining the exact match logic with range check logic (comparing lower and upper bounds) within the same cell, the system achieves range matching capability without requiring additional separate entries, thus preserving TCAM capacity.
2Adaptability or versatility
If multiple TCAM entries are used for each range filter, then range filtering is enabled, but power consumption increases
Solution Approach 1:
The patent merges multiple functions (exact match and range match) into a single TCAM entry, reducing the total number of entries required. This consolidation directly reduces power consumption since fewer entries need to be maintained and accessed, while still providing comprehensive range filtering capability.
3Device complexity
If conventional packet filters with limited number are used, then implementation is simple, but scaling to high packet processing rates is inefficient
Solution Approach 1:
The patent replaces conventional sequential packet filtering mechanisms with parallel TCAM-based matching. By substituting the traditional filter processing approach with hardware-accelerated TCAM operations that support parallel comparisons, the system achieves high packet processing rates while maintaining relatively simple implementation through the use of established TCAM architecture.
Data Source
AI summary
A multi-functional match cell is responsive to first and second n-bit operands and configured so that the match cell operates as an n-bit range match cell when the first and second n-bit operands are equivalent, as an n-bit NOR-type CAM cell when the second n-bit operand is masked and as an n-bit NAND-type CAM cell when the first n-bit operand is masked, where “n” is a positive integer greater than one.