PEDS: A Parallel Error Detection Scheme for TCAM Devices

A. Bremler-Barr, D. Hay, D. Hendler, R. M. Roth
2009 IEEE INFOCOM 2009 - The 28th Conference on Computer Communications  
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
more » ... fficulty 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-detecting 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 in a manner that is typically orders of magnitude smaller than the 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.
doi:10.1109/infcom.2009.5062044 dblp:conf/infocom/Bremler-BarrHHR09 fatcat:rgtnzxfvbrahzhwjm6pq767bye