Soft-Error Tolerant TCAMs for High-Reliability Packet Classifications

In the internet, packets are classified by source and destination addresses, ports, and protocol type. Ternary content addressable memories (TCAMs) are often used to perform this operation. However, high-reliability packet classifiers in aerospace network applications require soft-error tolerant TCAMs to prevent system from errors caused by environmental factors such as high-energy radiations. This paper shows a soft-error tolerant TCAM (STTCAM), which enhances the reliability of TCAMs for soft-errors. The STTCAM randomly selects a search key to be evaluated. Then, parallel TCAMs detect single-bit flip errors. When the search key matches the last word, the STTCAM calculates the similarity of the search key to the TCAM word. If 99% of similarity is detected, then a suspected error is found and the STTCAM refreshes the TCAM words by using a backup ECC-SRAM. Experimental results show that the STTCAM improves TCAMs reliability significantly than the existing scheme. The STTCAM can be easily implemented and is useful for fault-tolerant packet classifiers.