Hardware search engines are faster than algorithmic approaches for search intensive applications. Also, the turnaround time of a hardware CAM would be highly deterministic while that of software would depend on how efficiently the search-tree balancing algorithm is implemented. However, software would results in low costs. Hybrid CAMS integrate the robustness of a hardware CAM while providing the flexibility of high degree of software programming.

Types of CAMs

Fundamentally, CAM’s are of two types binary and ternary. As the name indicates a binary CAM has two bit states (’1′ and a ’0′), while a ternary CAM has ’1′, ’0′ and a third state called “don’t care”, so a search-hit on a ternary CAM would be an exact match or a partial match.

Currently, ternary CAMs are defacto in the industry. These bring the possibility of multiple match in a lookup table. All the access list tables for packet forwarding use a popular address resolution algorithm called the longest prefix match where the addresses are placed in the CAM based on certain priorities and the CAM by itself has priority encoder that helps in resolving the winning address.