HEXA: Compact Data Structures or Faster Packet Processing

1. HEXA: Compact Data Structuresor Faster Packet Processing Author: Sailesh Kumar, Jonathan Turner, Patrick Crowley, Michael Mitzenmacher. Publisher: ICNP 2007 Presenter: Yu-Ping Chiang Date: 2009/02/10

2. Outline • HEXA (History-based Encoding, eXecution and Addressing) • Main idea & example • One-to-one mapping • Update method • bHEXA (Bounded HEXA ) • Main idea & example • Experimental Evaluation

3. HEXA - Main idea & example • Standard representation: • Assume next hop information stored in shadow trie. • Fast memory consumption in this example: • 1(prefix flag) + 4(left child id) + 4(right child id) = 9 bits/node

4. HEXA - Main idea & example • HEXA representation: • Using path as node id • Fast memory consumption in this example: • 1(prefix flag)+1(left child exist)+1(right child exist)= 3 bits/node

5. HEXA - Main idea & example IP: _11010…. • Search operation Not prefix node & right child exist CINTINUE!!

6. HEXA - Main idea & example IP: 11010…. • Search operation prefix node & right child exist CINTINUE!! (longest prefix next hop = P1)

7. HEXA - Main idea & example IP: 11010…. • Search operation prefix node & left child not exist STOP!! (longest prefix next hop = P3)

8. HEXA - One-to-one mapping • discriminator • c bits → at most memory location can choose • HEXA ID = discriminator + historical path • Information for binary trie: 1(prefix flag)+c(left child discriminator)+c(right child discriminator) = 2c+1 bits/node • Hash: • (Discriminator, Id padding zero, Length) • mod 9

10. HEXA - Update method • Deletion: • Simply remove relevant node from hash table. • Insertion: • If corresponding position already taken →Find an augmenting path, and remap other nodes to other locations.

11. Outline • HEXA (History-based Encoding, eXecution and Addressing) • Main idea & example • One-to-one mapping • Update method • bHEXA (Bounded HEXA ) • Main idea & example • Experimental Evaluation

12. bHEXA - Main idea & example • Standard representation: • 1(match flag) + 3*4(node id) = 13 bits/node

13. bHEXA - Main idea & example • bHEXA representation • Examine a variable but finite number of symbols in history to identify a node • k transition away from root →id up to k symbol • 1(match flag) + 3*2(id length) = 7 bits/node

14. bHEXA - Main idea & example

15. bHEXA - Main idea & example h = 1*1 = 1

16. bHEXA - Main idea & example

17. bHEXA - Main idea & example

18. bHEXA - Main idea & example

19. bHEXA - Main idea & example Pattern: _a b c a…… • Match operation ( 0*0 ) mod 10 = 0

20. bHEXA - Main idea & example Pattern: ab c a…… • Match operation ( 1*1 ) mod 10= 1

21. bHEXA - Main idea & example Pattern: a bc a…… • Match operation ( 1*1 + 2*2 ) mod 10 = 5

22. bHEXA - Main idea & example Pattern: a b ca…… • Match operation ( 1*2 + 2*3 ) mod 10 = 8

23. bHEXA • Practical consideration: long path with same symbol • Let length bits indicate superlinear increment of id length • Employ a small on-chip CAM to store – spill fraction.

24. Outline • HEXA (History-based Encoding, eXecution and Addressing) • Main idea & example • One-to-one mapping • Update method • bHEXA (Bounded HEXA ) • Main idea & example • Experimental Evaluation

25. Experimental Evaluation • For ip lookup - Binary trie

26. Experimental Evaluation • For ip lookup - Multi-bit trie Improve only pointers to child to child’s discriminator. So less improve in large stride.

27. Experimental Evaluation • For ip lookup - Incremental update

28. Experimental Evaluation • For pattern match Cisco622 contains a string that repeat a same symbol 50 times.

29. Experimental Evaluation • For pattern match