TCAM Range Encoding via Overlapping Positive and Negative Entries
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Solution Overview
Problem
Ternary content addressable memory (TCAM) systems face challenges in efficiently encoding and prioritizing overlapping ranges for effective data storage and retrieval, particularly in network switching applications, where range encoding techniques do not always optimize storage entry usage and priority assignment.
Innovation Solution
The method involves determining first positive and negative ranges corresponding to an encoding range, encoding these ranges in TCAM entries with prioritization, and associating them with specific actions, such as a reject action, to optimize storage and retrieval processes by using overlapping encoding techniques that minimize the number of TCAM entries required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If non-overlapping encoding technique is used to encode the first encoding range, then the encoding is simple and straightforward, but the number of TCAM entries required increases
Solution Approach 1:
The patent merges overlapping positive ranges and negative ranges into a unified encoding structure. By allowing ranges to overlap and using a single TCAM entry to represent multiple overlapping ranges through priority-based matching, the system reduces the total number of entries required compared to non-overlapping encoding where each range would require separate entries.
Solution Approach 2:
The patent introduces dynamic priority assignment to TCAM entries based on their position and overlap relationships. Higher priority is assigned to entries with greater overlap extent or more critical matching requirements, enabling the system to adaptively manage range encoding efficiency and minimize entry count while maintaining correct matching behavior.
2Quantity of substance
If overlapping ranges are encoded in TCAM entries without priority assignment, then storage entry usage is reduced, but data retrieval accuracy deteriorates due to ambiguous matching
Solution Approach 1:
The patent performs preliminary priority assignment to TCAM entries during the encoding phase, before actual data retrieval occurs. By pre-establishing the priority hierarchy based on range overlap characteristics and matching requirements, the system ensures that when multiple ranges overlap, the correct entry is selected first, maintaining retrieval accuracy while using fewer entries.
Solution Approach 2:
The patent implements a feedback mechanism where the matching result from higher priority entries influences the evaluation of lower priority entries. When a high-priority entry matches, it suppresses or overrides potential matches from lower-priority overlapping entries, ensuring accurate retrieval while allowing the use of overlapping ranges to reduce total entry count.
3Productivity
If first negative ranges overlap with second encoding range, then the first encoding range can be encoded efficiently, but conflicts arise with the second encoding range associations
Solution Approach 1:
The patent applies local quality by assigning different priority levels and action associations to different portions of overlapping ranges. When first negative ranges overlap with second encoding ranges, the system locally adjusts the priority and action assignment for the specific overlapping region, ensuring that the correct action is taken for each local matching scenario while maintaining overall encoding efficiency.
Solution Approach 2:
The patent segments the encoding space by dividing overlapping ranges into distinct priority levels and action categories. First positive ranges, first negative ranges, and second encoding ranges are segmented into different priority groups, allowing efficient encoding within each segment while resolving conflicts at segment boundaries through priority-based resolution.
Data Source
AI summary
Aspects of the disclosure provide a method for encoding ranges in a ternary content addressable memory (TCAM). The method includes determining first positive ranges and first negative ranges corresponding to a first encoding range to be encoded in the TCAM. The first encoding range is in association with a first action. The first positive ranges include the first encoding range. The first negative ranges exclude the first encoding range. At least a first positive range and a first negative range are overlapping. Further, the method includes encoding the first positive ranges in first TCAM entries, and encoding the first negative ranges in second TCAM entries. At least one of the second TCAM entries has a higher priority than one of the first TCAM entries. Then, the method includes associating the first TCAM entries to the first action, and associating the second TCAM entries to a reject action.