Cementing High Availability in OpenFlow with RuleBricks Dan Williams - PowerPoint PPT Presentation

Cementing High Availability in OpenFlow with RuleBricks Dan Williams & Hani Jamjoom IBM T. J. Watson Research Center

Planning For Failure Shift towards highly elastic applications Failure is elasticty's evil twin e.g., "Chaos Monkeys" by Netflix 2

Focus on One Question How can high availability policies be added to OpenFlow’s forwarding rules?

Assumed Environment Replicas VM 1 VM 2 VM N Controller Flow reassignment if VM 2 fails Active OpenFlow Switch Rule Set Backup plan Flows 4

Goals Embed failure plans in existing environments Limit flow reassignments Limit rule explosion Keep it simple 5

Exploit Two Features Hierarchical structure of OpenFlow’s wild card rules Precedence rule execution 6

Brick Representation Binary Tree Bricks 01* 00* * 1* 0* = * 1* 0* IP address space 00* Brick width signifies address 01* coverage Number of bricks depend on width of bricks 7

Flow Assignment Flows a b c d Flows matching 0* will be assigned 110* to GREY replica 10* 1* 0* * Use color to represent replica assignment 8

Active vs. Backup Rules Flows a b c d e 110* Active rule set 0* 10* 1* 01* 00* * Flows will match top bricks 9

Remember Tetris? 3 operations in RuleBricks 10

VM 3 VM 1 VM 2 3 replicas, note their color 11

#1. Drop Flows matching 000* will be assigned to WHITE replica Flows a b c d 101* 000* 100* 111* 10* 0* 1* 01* 00* * Add VM3, WHITE replica 12

Reassignment on Failure c d Flows a b e 000* 101* 100* 111* 10* 00* * VM2 dies, GREY bricks vanish 13

#2. Insert Flows a b c d e 101* 100* 10* 111* 000* 0* 1* 01* 1* 00* * Set WHITE to take over GREY's portion of 1* 14

#3. Reduce Transformations defragment 10* 101* 100* fragment 101* deduplicate 101* 101* 101* 101* duplicate 101* 101* Use a greedy algorithm that frags/defrags, then dedups starting with least exposed brick 15

Example Start: 1.Fragment: 101* 101* 10* 101* 100* 1* 11* 101* 100* 1* 11* 101* 100* 2.Deduplicate: 3.Defragment: 100* 100* 11* 101* 100* 1* 11* 101* 100* 1* 16

What Can We Do With RuleBricks? Encode Chord's assignment policy Hash-based assignment of nodes on a ring, representing the IP address space When a node is removed, successor node takes over 17

Encode Node Replica Chord ring: RuleBricks: 11* 00* * 01* 10* covers the entire IP address space 18

Adding a Replica active rule 11* 00* 00* * * 01* 10* backup rule Drop active rule bricks Insert backup rule bricks 19

Adding a Third Replica active rules 00* 11* 00* 100* 01* 00* * * 101* * 01* 100* 20

Adding a Virtual Node 00* 01* 00* 11* 00* 100* 01* 00* * * 101* * 01* * 100* 21

Reducing Rules 00* 11* 00* 0* 100* 0* * 101* * 01* * 100* 22

Implementation Implemented RuleBricks in Python Looked at rule explosion for active rule set Looked at implication of having fixed vs. variable size bricks Fixed-sized RuleBricks 01* 00* 01* 00* Variable-sized RuleBricks 23

Brick-based Rule Reduction Use 16 virtual nodes per replica 24

Conclusion Failure is elastcity’s evil twin RuleBricks simplifies planning for failure RuleBricks can embed different flow assignment policies 25