1. 1 A Heuristic and Hybrid Hash- based Approach to Fast Lookup Author: Gianni Antichi, Andrea Di Pietro, Domenico Ficara, Stefano Giordano, Gregorio Procissi, Fabio Vitucci Publisher: 15th IEEE Workshop on High Performance Switching and Routing (HPSR), 2009 Presenter: Hsin-Mao Chen Date:2009/9/16

2. 2 Outline Introduction Background H-cube Idea H-cube Data Structures H-cube Search Performance

3. 3 Introduction From lookup tables, there is a large prefix disparity of density within each lookup table. The IP lookup problem can be the adoption of a Heuristic and Hybrid Hash-based technique.

4. 4 Introduction Heuristic and Hybrid Hash-based (H-cube), where different data structures store different prefix ranges according to their density.

5. 5 Background Perfect Hash Function (PHF) A perfect hash function maps a static set of n keys into a set of m integers without collisions, where m is greater than or equal to n.

6. 6 Background Minimal Perfect Hash Function (MPHF) A minimal perfect hash function is the same as perfect hash function. If m is equal to n, the function is called minimal perfect hash function.

7. 7 H-cube Idea

8. 8 H-cube Data Structures 23-24(MPHF 24 ) (1)For the range, we use a MPHF realized by means of Blooming Trees. Avoiding collision, each entry of such a table stores also the first 24 bits of the relative IP destination address. (2)To be able to use such a binary search, the range 25-32 we insert in the MPHF 24 a 24 bit- long rule and a bit b which signals whether more specified rules are in the range 25-32.

9. 9 H-cube Data Structures 17-22,25-32(PHF 22,PHF 32 ) For the range, we use a PHF obtained by double hashing. Each entry stores the first 22(32) bits of the relative IP address to solve potential collisions.

10. 10 H-cube Data Structures 1-16(DA 16 ) In this range, the number of possible rules is limited(2 16 ), a direct addressing table can be used.

11. 11 H-cube Data Structures

12. 12 H-cube Search

13. 13 Performance Constructing time and memory

14. 14 Performance Average number of accesses in SRAM and scratchpad for lookup

15. 15 Performance Memory consumption

16. 16 Performance Memory accesses