TCAMChecker: A Software Approach to the Error Detection and Correction of TCAM-Based Networking Systems

Ternary content addressable memories (TCAMs) are widely used in network devices carrying out the core operation of single-operation lookups. TCAMs are the core component of many networking devices such as routers, switches, firewalls and intrusion detection/prevention systems. Unfortunately, they are susceptible to errors caused by environmental factors such as radiation. TCAM errors may have significant impact on search results. In fact, only one error in a TCAM can cause 100 % of search keys to have wrong lookup results. Therefore, TCAM error detection and correction schemes are needed to enhance the reliability of TCAM-based systems. All prior solutions require hardware changes to TCAM circuitry and therefore are difficult to deploy. In this paper, we propose TCAMChecker, the first software-based solution for TCAM error detection and correction. Given a search key, TCAMChecker probabilistically decides to verify the lookup result. If TCAMChecker decides to verify the lookup result then it performs two parallel lookups for the given search key. If the lookup results do not match then at least one error is detected and is corrected by using a backup error-free memory. Note that the probability of lookup verification can be tuned for tradeoff between performance and reliability. A higher probability of lookup verification provides a more reliable TCAM system at the cost of performance. Our proposed TCAMChecker can be easily deployed on existing TCAM-based networking devices to improve the system reliability.