Ternary content-addressable memory (TCAM) devices are increasingly used for performing high-speed packet classification. A TCAM consists of an associative memory that compares a search key in parallel against all entries. TCAMs may suffer from error events that cause ternary cells to change their value to any symbol in the ternary alphabet “0”,”1″,”*”. Due to their parallel access feature, standard error detection schemes are not directly applicable to TCAMs; an additional difficulty is posed by the special semantic of the “*” symbol. This paper introduces PEDS, a novel parallel error detection scheme that locates the erroneous entries in a TCAM device. PEDS is based on applying an error-detection code to each TCAM entry, and utilizing the parallel capabilities of the TCAM, by simultaneously checking the correctness of multiple TCAM entries. A key feature of PEDS is that the number of TCAM lookup operations required to locate all errors depends on the number of symbols per entry rather than the (orders-of-magnitude larger) number of TCAM entries. For large TCAM devices, a specific instance of PEDS requires only 200 lookups for 100-symbol entries, while a naive approach may need hundreds of thousands lookups. PEDS allows flexible and dynamic selection of trade-off points between robustness, space complexity, and number of lookups.
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@INPROCEEDINGS{5062044, author={Bremler-Barr, A. and Hay, D. and Hendler, D. and Roth, R. M.}, booktitle={IEEE INFOCOM 2009}, title={PEDS: A Parallel Error Detection Scheme for TCAM Devices}, year={2009}, volume={}, number={}, pages={1296-1304}, doi={10.1109/INFCOM.2009.5062044}