Low%20Power%20TCAM%20Forwarding%20Engine%20for%20IP%20Packets

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Low Power TCAM Forwarding Engine for IP Packets
Authors Alireza Mahini, Reza Berangi,
Seyedeh Fatemeh and Hamidreza Mahini
Presenter Yi-Sheng, Lin (???) Date Aug. 12,
2008 Publisher/Conf. Military
Communications Conference, 2007. MILCOM 2007.
IEEE
Dept. of Computer Science and Information
Engineering National Cheng Kung University,
Taiwan R.O.C.
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Outline

1. Introduction
2. Proposed Approach
3. Proposed Architecture
4. Lookup operation
5. Update Operation
6. Performance Evaluation
7. Conclusion

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Introduction

• The works main objective is a TCAM-based router
  architecture that consumes less power.
• The existing approaches reduce power either by
  routing table compaction or selecting a portion
  of the TCAM.
• The authors reduces power by combining the two
  approaches.
• MLET MultiLevel Enabling Technique.

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Proposed Approach(1/4)

• Routing table minimization
• 1. Elimination of overlapped prefixes.
• 2. Partitioning the result of previous
  step into
• PRTs (Partial Routing Tables).
• 3. Minimizing the PRTs using Espersso
• Minimization Units (EMU) in
  parallel.
• 11 R. Lysecky and F. Vahid, On-chip logic
  minimization, In Proceedings of the 40th
  conference on Design automation, ACM Press, 2003,
  pp 334337.

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Proposed Approach(2/4)
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Proposed Approach(3/4)

• Overlap elimination
• 1. Pa lt Pb.
• 2. Pa,i Pb,i for all 1 lt i lt Pa.
• 3. There is no prefix Pc such that Pa lt Pc lt
  Pb, and Pc,i Pb,i for all 1 i Pc .
• Example
• Pa 1 0 1 0 1 0 0 0 port A
• Pb 1 0 1 0 port A

A
A
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Proposed Approach(4/4)

• Route Table Partitioning and PRTs
• The partitioning rule is very straightforward.
  It partitions the prefixes based on their
  corresponding output port.
• EMU ( 11 )
• Prefix
• 10011100
• 10001100
  

1001100
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Proposed Architecture(1/2)
10 11 01 01 10 1 11 00 1 10 01 00 10
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Proposed Architecture(1/2)

• The separator unit (SU) extracts the destination
  IP address of incoming packet.
• After IP address extraction and splitting, the
  split parts of IP address is stored into the Data
  Registers (DRs).
• ES signals are Enabling Signals of each stage in
  rows.
• ML signals are Match Line signals which are
  placed in the output of the last stage determine
  which row is matched with destination IP address.
• The LPM selector unit, dose the Longest Prefix
  Matchingselection.

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Lookup operation

• The time complexity of
• lookup operation is O(k).
• (K is number of stages)

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Update Operation

• Insert
• 1. According to the output port of pi prefix
  which is qi ,the
• start and end addresses of PRTqi got from
  Merger Unit.
• 2. the PRT entries with new pi sent to the
  related EMU.
• 3. Finally rebuilding of the table and saving the
  new addresses must be done.
• Delete
• The algorithm for removing a prefix from the
  routing table is more complex because the problem
  of prefix covering.

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Performance Evaluation(1/4)

• EPS (Enabled bits Per Search) power consumption
  in lookup operation directly depends on the
  number of enabled bits of TCAM table cells.
• MEPS (Mean Enabled bits Per Search)
• m number of lookup times

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Performance Evaluation(2/4)

• POF (Power Optimization Factor)

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Performance Evaluation(3/4)
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Performance Evaluation(4/4)
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Conclusion

• A power efficient TCAM based hardware
  architecture has been proposed.
• The power consumption is found to be remarkably
  low to promise efficient TCAM design in the future