Efficient TCAM Encoding Schemes for Packet Classification using Gray Code

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Efficient TCAM Encoding Schemes for Packet
Classification using Gray Code
Authors Yeim-Kuan Chang and Cheng-Chien
Su Publisher the IEEE Globecom 2007
conference Present Chen-Rong Chang Date
December, 10, 2008
Department of Computer Science and Information
Engineering National Cheng Kung University,
Taiwan R.O.C.
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Outline

• Introduction
• Related Works
• Proposed range encoding shemes
• Performance

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Introduction

• A traditional solution for storing ranges in
  TCAM is the direct range-to-prefix conversion
  which individually converts each range into
  multiple prefixes.
• A set of encoding schemes called parallel packet
  classification encoding (PPCE) is proposed based
  on the concept of elementary intervals.

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Elementary intervals
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Direct range-to-prefix Elementary
interval-based encoding scheme
Direct range-to-prefix conversion EX R2 2
6 0 0 0 1 0 0 0 0 1 1 0 0 1 0 0 0 0
1 0 1 0 0 1 1 0 Elementary interval-based
encoding scheme EX R2 1 1 0 0 0 1 R3
4 7 0 1 0 0 0 1 0 1 0 1 1 0 0 1 1 1
For tatal 17 5-bit prefix
0 0 0 1
0 0 1 0
0 0 1 1 0
For tatal 6 4-bit prefix
0 1
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Parallel packet classification encoding (PPCE)
scheme
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Proposed Range Encoding Schemes
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Proposed Range Encoding Schemes (cont.)
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BRGC range group

• The following rules are satisfied
• no range is disjoint from the other ranges in the
  group
• each range covers exactly consecutive
  elementary intervals
• the identifiers assigned to these intervals can
  be merged into one ternary string
• Perfect range group
• it covers 2d 1 valid elementary intervals
  which need 2d 1 distinct identifiers.

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Perfect BRGC range group (cont.)
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Imperfect BRGC range groups
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Many-to-one code assignment

• The many-to-one code assignment scheme achieves
  the goal of using only one ternary string to
  encode a range by assigning more than one code to
  an elementary interval.

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One-to-many code assignment

• The one-to-many code assignment scheme extends
  the use of a common code from the default
  elementary intervals to the valid elementary
  intervals by assigning a common code to the valid
  elementary intervals covered by the same subset
  of original ranges

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Performance
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Performance (cont.)