Document Type
Technical Report
Publication Date
2004-07-06
Technical Report Number
WUCSE-2004-39
Abstract
TCAMs are the most popular practical approach to high performance packet classifica-tion, but they suffer from inefficient handling of range matches; the standard approach of rule replication can result in a 2-6x increase in TCAM words needed, for typical firewall databases. We describe three CMOS implementations of a range check circuit to address this problem; the most efficient of these designs allows classification on the standard IPv4 5-tuple with only a 46% increase in transistor count, rather than relying on rule replication. By avoiding replication, the overall transistor count required is only 24% to 78% of the stan-dard TCAM design, for real filter databases used in this study; power dissipation is reduced similarly. Also, range check support greatly simplifies creation and maintenance of the TCAM contents, since there is now a one-to-one correspondence between filters and TCAM entries. Additionally, we show how to construct a more versatile device using range-check sub-fields that can be chained together as needed.
Recommended Citation
Spitznagel, Edward W., "CMOS Implementations of a Range Check Circuit" Report Number: WUCSE-2004-39 (2004). All Computer Science and Engineering Research.
https://openscholarship.wustl.edu/cse_research/1012
Comments
Permanent URL: http://dx.doi.org/10.7936/K7XP7380