PEDS: A parallel error detection scheme for TCAM devices

Anat Bremler-Barr*, David Hay, Danny Hendler, Ron M. Roth

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


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-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 of lookups. PEDS allows flexible and dynamic selection of tradeoff points between robustness, space complexity, and number of lookups.

Original languageAmerican English
Article number5454422
Pages (from-to)1665-1675
Number of pages11
JournalIEEE/ACM Transactions on Networking
Issue number5
StatePublished - Oct 2010
Externally publishedYes

Bibliographical note

Funding Information:
Manuscript received December 04, 2009; accepted March 21, 2010; approved by IEEE/ACM TRANSACTIONS ON NETWORKING Editor D. Towsley. Date of publication April 26, 2010; date of current version October 15, 2010. Patent pending. This work was supported by a research grant from Cisco Systems, Inc. A. Bremler-Barr is with the Efi Arazi School of Computer Science, The Interdisciplinary Center, Herzliya 46150, Israel (e-mail: D. Hay was with the Computer Science Department, Ben-Gurion University, Be’er Sheva 84105, Israel. He is now with the Electrical Engineering Department, Columbia University, New York, NY 10027 USA (e-mail: D. Hendler is with the Computer Science Department, Ben-Gurion University, Be’er Sheva 84105, Israel (e-mail: R. M. Roth is with the Computer Science Department, Technion—Israel Institute of Technology, Haifa 32000, Israel (e-mail: Color versions of one or more of the figures in this paper are available online at Digital Object Identifier 10.1109/TNET.2010.2047730


  • error detection
  • error-correcting codes
  • error-detecting codes
  • packet classification
  • ternary content-addressable memory (TCAM)


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