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MIPS Extension for a TCAM Based Parallel Architecture for Fast IP

Lookup

Author:Oğuzhan ERDEM Cüneyt F. BAZLAMAÇCI

Publisher:ISCIS 2009

Presenter:Po Ting Huang

Date:2010/4/14

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Introduction

Architecture on Akhbarizadeh et al. [9] We observe that the main problem of the architectur

e proposed in [9] is the potentially time consuming cache update process since the system must calculate the minimum expansion prefix (MEP) of the corresponding prefix((2+w)cycles,w=32 for ipv4)

by using minimum independent prefix set (MIPS) algorithm→easing the cache updates and decreasing the number of contentions.

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Outline

Introduction TCAM based parallel architecture for fast iplookup MIPS based forwarding table MIPS integration in TCAM based parallell forwarding

engine Performance Evaluation of MIPS Performance Evaluation of MIPS Enhanced Parallel

Architecture

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TCAM based parallel architecture for fast iplookup

MSMB:multiselector- multi-block prefixes are divided into ranges, each range of prefixes is store

d in a separate TCAM block and range detectors (RDs) are used to select the appropriate partitions.

PPM(private prefix memory):is used to store the most popular prefix as a TCAM cache

Contention:When two or more packets are destined to the same TCAM unit, contention occurs.

CR(contention resolver):when contention occur,CR lets only one of the requests to proceed and puts the rest of the requesting selectors on hold.

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In order to prevent contentions PPM is used and all PPM units, one per selector, have identical content.

Contentions are used as indicators for the existence of popular prefixes

MEP(minimal expansion prefix):A parent prefix is not allowed in PPM since the forwarding engine must always choose the longest matching prefix

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MEP process

consider a given search key as 10110 and its matching prefix as p=10*.

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MIPS based forwarding table

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MIPS integration in TCAM based parallell forwarding engine

The update process of a PPM unit is triggered whenever a contention occurs and no other update request is accepted until the current one terminates

coherence between PPM units and TCAM units are to be preserved when the periodic updating process of TCAM units

inserting:creat parant in PPM

deleting:spend time to find corresponding MEP in PPM The prefix entries are maintained in sorted order in TCAM modules

because the existence of the priority encoder

maintaining the order of TCAM entries brings an update

complexity requiring shifting of TCAM entries for insertion and

deletion.

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■

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adopt MIPS based trie to the architecture instead of using the originally proposed PATRICIA trie

→ MEP finding process is eliminated →coherency between the forwarding table and the PPM unit is always

maintained →the need to sort the TCAM entries is eliminated. →there is no need for the output priority encoder

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Performance Evaluation of MIPS

compression ratio is calculated as [(original table size – MIPS table size) / (original table size)] x100..

randomly generated routing tables based on Gaussian prefix length distributions.

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Performance Evaluation of MIPS

Three real life back bone routers

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Performance Evaluation of MIPS Enhanced Parallel Architecture

The number of contentions

and hold conditions

decrease approximately

by 30%. PPM match increase TCAM search decraese

Energy efficiently