MIPS Extension for a TCAM Based Parallel Architecture for Fast IP Lookup

1. 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

2. Introduction • Architecture on Akhbarizadeh et al. [9] • We observe that the main problem of the architecture 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.

3. 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

4. TCAM based parallel architecture for fast iplookup • MSMB:multiselector- multi-block • prefixes are divided into ranges, each range of prefixes is stored 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.

5. 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

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

7. MIPS based forwarding table

8. 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. ■ ■

9. 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

10. 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.

11. Performance Evaluation of MIPS • Three real life back bone routers

12. 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