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CoPTUA: Consistent Policy Table Update Algorithm for TCAM without Locking
December 2004 (vol. 53 no. 12)
pp. 1602-1614
Due to deterministic and fast lookup performance, Ternary Content Addressable Memory (TCAM) has recently been gaining popularity in general policy filtering (PF) for packet classification in high-speed networks. However, the PF table update poses significant challenges for efficient use of TCAM. To avoid erroneous and inconsistent rule matching, the traditional approach is to lock the PF table during the rule update period, but table locking has a negative impact on data path processing. In this paper, we propose a novel scheme, called Consistent Policy Table Update Algorithm (CoPTUA), for TCAM. Instead of minimizing the number of rule moves to reduce the locking time, CoPTUA maintains a consistent PF table throughout the update process, thus eliminating the need for locking the PF table while ensuring correctness of rule matching. Our analysis and simulation show that, even for a PF table with 100,000 rules, an arbitrary number of rules can be updated simultaneously within 1 second in the worst case, provided that 2 percent of the PF table entries are empty. Thus, CoPTUA enforces any new rule in less than 1 second for practical PF table size with high memory utilization and without impacting data path processing.

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Index Terms:
Network processor, ternary CAM, policy table update, packet classification.
Zhijun Wang, Hao Che, Mohan Kumar, Sajal K. Das, "CoPTUA: Consistent Policy Table Update Algorithm for TCAM without Locking," IEEE Transactions on Computers, vol. 53, no. 12, pp. 1602-1614, Dec. 2004, doi:10.1109/TC.2004.108
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